Just some questions

So I have a rabbit who is around 7 months old and we think is a rex rabbit because he has curly whiskers and such, but he is BIG. At around 6 months we weighed him and he was 9 pounds. He has definitely grown since. Why is he so big? we're feeding him the recommended amount on his food bag, he has unlimited hay because I've heard that's what they should have, and he gets some lettuce everyday, so I don't think we're overfeeding, unless we are which I'll try and fix. He also doesn't feel fat, mostly muscle and skin lol.

My other questions are how to bond more with him? he grooms me sometimes, and seeks me out for cuddles occasionally, likes being held, as in falls asleep in my arms, I usually only hold him when needed but sometimes when he's being cuddly ill pick him up and he'll take a nap.

Also he's ALWAYS breathing fast??? even when asleep he breathes quickly. It sounds like he's scared but it's always?

And he uses a litter box but he still poops outside of his cage half the time? and he pees on this one spot for no apparent reason? he was ONLY using his litter box for a solid couple of weeks other than the occasional turd here and there but then suddenly started pooping everywhere.

And he has an obsession with our one cat? we have three that he is ok with and plays with and stuff. one cat hates him from afar, one plays with him and sometimes sleeps with him, but one he's REALLY close with.

They cuddle, sleep together, groom each other, just bffs it seems, but when she was in heat she kept trying to shove her butt in his face, which when I would see it I would Separate them, but then they would run off to under my bed and he would hump her (which BTW he has terrible aim, he would end up just humping her legs) and I would Separate them for around 5 minutes to half an hour depending on how long it take for him to put his wee away. I would always stop them but my parents found it funny and would let them. Now she's not in heat and my other cat is but he doesn't like her like that I guess lol. Now he keeps humping the cat he's buddies withs face. Legit her face. And the cat in heat keeps humping him, like biting his neck and side stepping while on top of him. Our cats are all female. Before him they would do that to each other. Now she's doing it to him. Idk how to get them all to stop??? help?? We can't afford neutering and fixing them rn.

Also our rabbit keeps doing hit and runs to my family. He runs over to them, bites wherever, then bolts. Why?? he doesn't do it to me but he does it to my mom dad and sister. ESPECIALLY my mom and sister. I don't think it's a gender thing cuz I'm bio female. I mean my mom treats him pretty bad as in not respecting his boundaries like when he doesn't want to be held, and she kicks him away from things and when she gets mad at him she slaps his butt, which I try to get her to back the f off. My sister is basically the same. My dad doesn't do that stuff though? he just yells at him cuz his poops are mainly centered around my dad's shoes and toolbox that never moves.

And for his cage I have a hutch/cage for him that is just his area to go to where the cats don't bug him and we humans don't bug him unless needed, also keeps his food and water Separate from the cats. He also is mainly freeroamed and when he's not we have a large dog xpen that I set up around his cage for nights and when I'm at school or leave the house. He lives in my room so I have a litter box for him in here and a water bowl just to be sure he's hydrated cuz he also has a water bottle. For him I want to have my room just be his room cuz it's hard having the play pen at night cuz I walk into it and it hurts also setting up and taking down is annoying. I want to have him in here usually but I also want my cats to be in here. any ideas how I can set it up? My cats can jump in and out of the playpen except for my-my cat, the cat who is pretty much just mine, she doesn't like my family, sleeps with me, follows me around, etc, and she is kinda dumb (said with love). She doesn't know how to leave the playpen, she just walks backwards. Legit won't walk forward when in there. and won't jump out or even stand on her hind legs. Just walks backwards repeatedly. We have to carry her out. so I can't have that just set up to keep him in here at night. Any ideas???

Also eventually, NOT SOON AT ALL, I want to get another rabbit. I originally wanted a lionshead rabbit, but my dad fell in love with this guy, who my dad basically ignores now and I care for. My dad originally got him for me as my personal pet but when my mom found out my dad bought a rabbit for me she's got pissy and forced it to be a family pet because of my younger sister being jealous. Now the "family" pet chores all fall on me, food, water, health checks, shit picking up, cage cleaning, all of it but I don't get to call him mine or have a say in how to train him. My mom is a violent person, used to beat me until I told the school, now she hits the cats and rabbit. I always get mad at her and try to educate her but she doesn't listen. Any help on how to get her to quit it??

That's all, sorry for the longggg post lol.