His coworker is being inappropriate. He needs to make it clear that he is not going to discuss anything not work related with her.

"My marriage is not a topic I'm going to discuss. Is there anything work related you need to talk about?"

At these work events he can excuse you both from sitting next to her. "Excuse us. We're going to mingle" or "I see John over there. I need to talk to him. Excuse us."

Move out with or without your boyfriend.

Then his life goals don't line up with yours. If he doesn't care that he doesn't make enough to cover his car payment and rent then odds are, he's never going to do much with his life.

If he wants to own his own gym someday, he will be too busy running a business to do any training. Running a gym would teach him the ropes of owning a gym. Also why couldn't he train people on his own time?

Change your number and delete your socials for awhile. He can't contact you if he doesn't have your phone number or socials.

There's a saying... You can put all the lipstick on a pig that you want but it's still a pig.

I can't think of a way to politely tell your mom that your dad told you you're not welcome because you won't subject yourself to your brother's craptastic behavior. It is what it is.

Tell her the truth. Tell her you're father told you that you were not welcome on the calls anymore because even though you're civil towards your brother, he can not manage to do the same so you refused to mend a relationship with your brother who is hateful towards you.