Liz, I'm so sorry to hear about your trip to Chicago and the way your DBF treated Remy on his birthday.

L (3andMe) covered much of what I wanted to say. I also want to give you a hug

because I know it's hard when you feel like you're the one constantly having to compensate for someone else's ... weak points... for lack of a better word. You try to be as big about it as you can... chalk it up to his depression, make allowances for it because of circumstances with his mom/job/etc. Those may all be very valid reasons for him to be self-absorbed and not the nicest person, and wherever you cut him slack is generous of you. However, at the end of the day, it's so draining to feel like you're pulling the whole bus, and it'd be nice to have someone who not only shares the load equally with you but steps in on days that you need someone to bear part of your load too. And it's hard when that person is off fighting his own demons. I've been there, mama.
It may make you not want to be there for him as his lover, and I don't think anyone would blame you. But maybe it'll give you strength in dealing with him to think of him as the father of your kids and he'll always need your help in that department; if you can help lift him out of depression, it will make him a better father, the kind who'd say Happy Birthday to his children. And they'd thank you for it if they knew.
Good luck and hang in there, Liz. Happy birthday, Remy!