Needing advice - TW possible toxic relationship

I’m F 27 and my son’s father is 35. He works full time and I am a full time college student headed towards law school. So I have a 10 month old and I’m thinking that my relationship with his father isn’t healthy and I’m wondering if it’s all in my head or if what’s going on really isn’t acceptable? My son’s father and I were together for a short time before I became pregnant and all seemed okay.He was excited and I was nervous. Then he began to snap at my often and cuss at me. He often refuses to watch the baby so I can do anything and has never done a night shift with the baby he also does not do household chores unless I ask, he also does not pick up or drop the kids at school who we have full time. He goes out on Wednesdays and Saturdays with his friends and I stay home and maybe go out once a month on a Saturday but with him because if I try to have a girls night he becomes angry and accuses me of wanting to cheat. I had to take his oldest to gymnastics this morning, and I was running late and had to wake him up since he was still asleep. as I handed him the baby for the hour and a half he watches him or helps with him a week I realize he’s poopy. I hand him the diaper and wipes trying to be helpful and he snaps at me “you can’t change him before you leave?” And I explain to him that I’m running late and I cannot. He then proceeds to tell me “you can’t change the f***** baby” and talking badly about me to the baby. I leave and slam the door. I hear him shout at the baby “STOP” because he was rolling and I go back in and tell him not to yell at the baby and that it’s unacceptable which he tells me “he’s my son I’ll yell at him if I want to” I leave in tears and take his oldest to gymnastics. He calls me while I’m there and “apologizes” for being angry and when I don’t immediately perk up he says “did you hear me?” And I said “you really hurt my feelings” he responds with “f*** you and f*** off” and hangs up. Then after gymnastics he had sent me a text saying the baby was breathing weird and to call him so I do and he proceeds to be like “oh the baby is fine was just breathing hard for like 30 seconds but I just would never leave you to Change the diaper the second you wake up” which he has done actually always does since he rarely changes him or does any of his care taking. This isn’t the first incident of him being aggressive or disrespectful and I feel as if I’m in a relationship I don’t belong in. He is now trying to be all lovey dovey and kiss me and spend time with me and I truly have no interest in being around him as I know within the week he will be disrespectful like this again. I have tried talking to him about his behavior and how it makes me feel and he refuses to go to therapy or work on it. He usually says “he’s always the bad guy and that I’m always b****ing about something”. The step kids depend on me because bio mom is a piece of work and only has supervised visits and dad works a lot and would rather hang with his friends or be on his game than spend quality time with them. But I worry if I stay that I will regret it and won’t be at 100% for my son as he grows up from being emotionally and physically exhausted from dealing with his father . So is it all in my head? Is this a normal relationship? Should I try to make things work for the kids?