Hi everyone. I need advice from folks who have insights into step family situations.

I have been in a five year relationship with a man who has two kids. We have been engaged for two of these years. We live together and he has 50/50 custody of his 7 and 5 year old. I am 41 years old and don't have children of my own. We've tried to have a baby but have been unsuccessful. The issue is I am miserable with this man especially when it comes to his kids. My partner is raising two entitled, emotionally manipulative children and our relationship and everything else revolves around them. They laugh at chores, say they hate one another and create messes and drama all day long. They scream nonstop, run on furniture, don't pick up after themselves, refuse to things that are asked. So they are misbehaving but on the other hand, they can be super sweet and very loving.
 

Ironically, I love them but tolerating their behavior is difficult for me. I blame their parents for this primarily as the kids were not raised with boundaries or respect. The issue is my partner does not see these issues, thinks this is normal behavior. For the duration of our relationship, he has made his children and what they want the center of it.

For instance, his children wanted a dog. Initially I was okay with it but then realized it would just another thing I would have to clean up after. My partner and kid kids are very messy and do not care to pick up after themselves even though I have told I get anxious in cluttered environments. I gave the dog a lot of thought and told him, I did not have the mental bandwidth for a puppy, my intense-high stress 60 hour a week job, and the 2 kids. I told him I would not stop them but I wanted him to know my feelings and that I would be unable to help with dog and that candidly, I did not think the kids would help with the dog. Well, he got the puppy and our home turned into a zoo. The kids rile up the dog but do not help with it at all. Between the kids, the dog, the pandemic, the relationship issues with my partner and my long work weeks, I reached a breaking point and took an actual leave from my job. I just could not handle it anymore. 
 

This is the background. This morning my fiancé was disrespectful to me (called me the b word) and said it was just a joke. I have told him countless times not to joke with me like this. Admittedly, he jokes in a very offensive and crude way. Towards me and everyone he is close enough to. I blew up at him, left the house and am at a friend's house right now.

I don't know what to do. My leave may turn into unemployment during a pandemic. I don't know if I can stay in this relationship. I'm 41 and hate that I'm failing at another relationship. I have a family support system and financially, I am able to move on from this.

Any advice?