So so tired....(rant/need advice on the kiddos)

I can't sleep more than an hour or so without waking up. Even if I manage to maybe sleep a little longer, one of the kids wake me up through the baby monitor and if it's my 6mo I have to go in for a feed. My 2 yr has been testing every friggen boundary and it's making me wanna pull my hair out. He used to be nice and gentle with the dog and now he's trying to hit, jump on, and ride her no matter how many times we show how to be gentle or take the dog to another space to try again later. He's now taken to spitting his drinks out everywhere, throwing things directly in our faces, hitting really really hard, and just over all pushing buttons. I've tried showing gentle touch, tried explanations in simple terms that what he's doing isn't ok while setting the proper example. I don't know what to do anymore and I want to break down. The only person in the house he's gentle with anymore is his 6mo sister. He gives her hugs, kisses, and toys. Unless it's her he's basically a tiny terror. I never get them to nap around the same time so I don't get to nap. I can't go to bed until midnight because her last feed before the 3hr stretches is 11:30pm so no point in sleeping before then. My 6mo is also going through a sleep regression so sometimes she'll be up every hour or she's up by 5:30am to stay awake 🥴. I am EXHAUSTED. My fiancée is trying so hard to help, he can't really take over night feeding cause I'm pretty much exclusively bf and he also get up hella hella early for work (i dont want him over exhausted too). He's taken up doing dishes after dinner to try and take off some stress since I would typically just leave it for me to do in the morning 😅. He's not a good cook so I almost always make dinner unless it's a Hamburger helper. He tries to let me sleep in more on the weekends but my body will physically not allow it if I hear the kids (especially if they're crying). He said I should try sleeping meds to help, but then I'm worried that I won't wake up if one of the kids need me on the monitor (more specifically the 6mo) since my Fiancée is a ridiculously heavy sleeper and wouldn't hear it himself. He helps out a lot more than this, but this is just a couple examples of what he does for me. I'm trying to play more and set more time aside for my son, I feel like I haven't been as present for him since his sister was born, to see if thay helps with the acting out. Maybe it's just terrible 2s? I don't know I just know I am physically and mentally tired all day everyday. We don't have the money for me to just go out and have a me day and that incudes just driving around since thats gas money we don't have, in fact we're late on all the "non essential" bills. Yet we "make too much" to qualify for ANY assistance. It's been rough financially, but soon it should be a little better. I don't know...thanks for reading.. if you have any tips on my toddler being a butthead than feel free to comment 😅 I'll try almost anything at this point.