Ladies, i need advice.

I’m a mother of two, i am 21 years old . I have a 3 almost 4 year old Daughter named Isabella and Baby girl who is on the way . I’m 35 weeks and just a couple days .. due December 17th two days before Isabellas birthday and i am happily married not to Isabellas father but to my best friend jon who has been around since day one he works sooo damn fucking hard and is incredible and has given me the world and has given me what I’ve got today i couldn’t be more grateful for him and what he does for Isabella and i .. as for Isabellas biological father we were together for about three years we been separated for about 2-3 years now I don’t know why i was so blinded by him and so stupid to not listen to anyone else when they told me he was no good he was my first when i mean first he stole my Virginity and i give that as my excuse to why i stayed so long but people don’t think it’s reasonable excuse because he’s cheated and abused me pregnant and all and i was just so damn stupid and people just say its not a reason to stay with someone like that i mean but he is the father of my child too and i was only 16 at the time but whatever it is what is it is now we aren’t really good with co-parenting because he is an idiot and is just shitty af we did settle things at court before i have sole custody and he gives child support every week of $110 (which he isn’t doing ) hes about $880 far behind and he gets to see her on weekends no over stays because he’s just disgusting and I wouldn’t be able to trust him with her over night he’s super unfit isn’t careful with her i always get her back a hot mess missing clothes socks , comes back with bruises and rashes doesn’t check her sugars count her carbs and I’ll explain in a bit what i mean by that .. And he is always hopping from home to home isnt now because he finally got a place with his sister and dumb girlfriend but you never know because clearly he Can’t keep up with child support and he’s a super huge pot head and always has a reason to not give me money and every where he has stayed i knew the person and they never charged him a damn dime he has no financial obligations no car which he had but not anymore not even a phone but a broken tablet he uses for wifi to talk to me on Facebook like we have no good communication if it were to be important about bell he would never hear from me because he’s never around wifi all the time and half of the things i deal with ;with Isabella I believe is because of him he doesn’t discipline her or teach her right from wrong he lets her do whatever she wants so when i get her back from him she comes home thinking she can do what she wants just like she does with him .. Isabella is a Diabetic type one and deals with a lot of medical and Educational issues and he doesn’t care i can message him about anything that has to do with her and he will read the message and not reply and if he does reply he will respond with an ok .. no question asked or anything and isabella does has evaluations set at school soon to go too for a couple of problems that she deals with such as Her behavioral issues , her speech etc and so basically she will be put in Special ed to help her .. she has Adhd Appointments coming soon as well gets the adhd from her father , we see her Endocrinologist for her Diabetes and will be seeing her cardiologist for the murmur she seems to have as well on top of everything else .. her father doesn’t show up or seem to care or ask questions about her school or any of her appointments which is annoying because i would be so concerned and hes not if i were him.. he’s been too worried focusing on the things that dont matter for example his girlfriend she and i dont get along what so ever and always seems to want to start problems with me tried hitting me 4 months pregnant before because i told her to mind her damn business because shes nosey and wants to be in everything and has spoken shit about Isabella saying that i dont know how to properly take of her basically blaming me for all her issues she has not been in the picture for long to tell me how my daughter is when she doesn’t know shit about her and what i go through with her on a daily because im with her all the time besides when shes in preschool..for 2 1/2 hours but any who he gives more attention to her and her son rather than Isabella but i do have court tomorrow for child support to get garnish and to set up times and location for when needed to pick up and drop off isabella i need advice because I’m slowly losing my mind because of how terrible things have been with Isabella shes been making things harder for jon and i on top of all the other shit we deal with financially and just in general and she has been acting horribly she’s not behaving in school she’s has more bad days than good days and to say that my childs been in the principles office multiple times because of her behavior sounds pretty insane for a 3 year-4 year old but i am not lying and it’s embarrassing to me and it’s embarrassing when she’s the only child being held on too when it comes to picking her up from school because she’s been uncontrollable and is just screaming or is running away from me ... when i say her behavior is terrible i mean the kicking the screaming the hitting teachers and students and throwing herself on the ground saying no to everyone just not listening to anyone doing whatever she wants is just unbearable and yeah yeahh people say oh shes a toddler she will grow out of it NO she’s always been this way but shes getting worse and worse as the days go by her own teacher feels so bad for me she asks me all the time how do i do it her teacher is amazing i love her and really tries her best with her.. but i see kids her age all the time and they never Act the way she does .. two weeks ago we had class training for her Dexcom monitor .. Dexcom is a glucose monitoring system which gives me more glucose readings and less finger pricking for sugar checks it comes with a transmitter and monitor and so the receiver lets me know when her sugars are high and low it will give me alerts and keeps track and with the sensor it measures glucose levels just underneath the skin and a transmitter that is fastened on top of the sensor and sends data wirelessly to the System receiver so we know how her sugars are when it comes to eating or anything so she and i go to the hospital and of course their are other kids with diabetes and there parents come as well to get on the monitor to make things a bit easier on us and There was a mother with 4 kids two twins and a son and daughter twins were babies and the son and daughter were id say 3-5 just around Isabellas age and when i tell you they were Angels they were like if they came out from a cloud from the sky super good sat down quiet listened while on the other hand my only child is not listening wouldn’t let the instructor speak didn’t stay in her seat screaming touching things and i was called out and had to reschedule and do a one on one because it was hard for the other parents to hear while Isabella spoke over instructor interrupted her and touched things so there was just no way to be able to set everything up with her acting the way she was .. even giving her anything to keep her still just didn’t work it does but doesn’t.. i was literally in tears because of how stressful and embarrassing it was .. and the crazy thing is is that you can never know when she is high or low before the dexcom she could be low 40s and be a energetic bunny she shows no symptoms whatsoever and it’s insane to me and it’s super rare when you can tell there something wrong with her .. and I just need to know if there’s any other mother out there who is dealing with this kind of situation or similar I don’t know what to do with her honestly like I feel like crying all the time she’s just so bad and anything I do as to trying to talk to her about what she does wrong putting her in timeout spanking her when it’s necessary it just doesn’t seem to work with her she doesn’t seem to get anything