Divorce mediation

Any advice from your own experiences is greatly appreciated. I have mediation in a few days for divorce/child custody and I am a nervous wreck! I have no idea what to expect. In the beginning of my seperation my ex and I were pretty cordial but now here we are iver a year later and finally going through the divorce and he has become pretty nasty. I have had a few consultations with an attorney and they have said they don't feel that I need a lawyer since I am not asking for anything really outlandish but I am so afraid of the unknown. Currently we have a 50/50 parenting plan but I feel that my children should be with me more since he pays no attention to them while they are there, he invites his gf over and they either sit up in his room or just take off and go shopping or whatever leaving my kids to roam the neighborhood or sit home alone. (They are 14&8 so nothing I can do legally.) my children also struggled with their grades as homework was due on Friday and Thursday Friday is his days and he wasn't having them complete and submit their homework for grading. He is never able to leave work early or take the day off when The kids are sick or have a half day which leaves me to miss work or make the arrangements for them to be picked up. I have always done everything for my family like staying home or not working a whole lot, all of the late night baby feelings and every Dr appointment, field trips, and arranging the after school care if I wasn't able to pick up so he could build his career. Now that hat we are separated I have moved out of our home because I couldn't afford to stay their in my own and had to get a full time job on top of continuing to make sure our kids are taken care of which has been hard for me without any real professional  experience  so I am asking for spousal support, child support, and I want 3 days a week and e/o weekend leaving him 1 day a week and e/o weekend.