Morning Kurt, your situation reminds me of a friend of mine whose husband started a new job with a "young, trendy, media-crowd" and turned in a matter of weeks from doting father and husband to a self-centred arsehole who spent every night on the lash with his new colleagues, and who felt "suffocated" by his previously happy married life.
In short it didn't end well, for him. They split up, he shagged around, got bored, begged to come back, they reunited and after some time tried for a baby at which point he infected her with quite a nasty STD which he denied was his fault as apparently he'd been completely faithful during their break-up.
The sleeping with other people whilst they were "on a break" my friend could have forgiven. The swearing on their daughter's life that he hadn't passed on the STD until finally admitting he had when my friend was so riddled with it she almost lost the ability to have any future kids, she could not forgive.
She is now happily living with a lovely new DP in their new house, and trying for a new baby, whilst her ex is in a small flat, still shagging anything he can and is thoroughly miserable by all accounts.
Some men seem to believe that they can turn their backs on family life when it suits them and live a bachelor lifestyle. Well he can, but that doesn't mean you have to wait in the wings whilst he does so.
I want to reiterate my earlier post and think you should tell him that he needs to fix some access times to see the kids, sort out some maintenance payments and start looking for somewhere else to live, because if he doesn't want in on family life you need the time and space to be able to find someone who does.
Make it 100% clear to him that you're not going to sit around twiddling your thumbs waiting for him to come to his senses when he has so clearly already checked-out of the relationship. (sorry for the mammoth post, got a bit carried away!)