A man who cheats on his wife & mother of his kids has a different mentality from you (or any decent, authentic person).
Likewise one who does it without even practising safe sex .... He's not even risk averse enough to protect himself against diseases. Immature, reckless, risky mentality (and ok with risking your health too).
There are lots of people who don't act like that.
Then there are people like him.
It's easy to say as an outsider but it's a waste of your time thinking "he doesn't even care enough" about someone who has the character to cheat on their wife of years and to not even use condoms. There are lots of things wrong with him.
There's no point in applying normal "rules" or expectations with someone so immoral, risk taking and degenerate. He obviously has sides to him that he's hidden from you (and his family) for years. You were not seeing the real him.
He's a front.
He's probably avoiding you now because he doesn't want to face up to any questions or face up to you possibly saying your relationship is over.
Anyway, with at least two STDs, likely contracted on the last month or so; there is clearly a lot going on in his life that he's hidden from you. Whether it's other partners, prostitute use, possibly even a gay sex life .. who knows.
He's made sure he's thought to be working til late every evening; but who knows where he's actually been and with whom.
You've got to consider that when thinking "where is he, "he doesn't seem to care" etc
He didn't see the marriage how you see it. He couldn't have acted like this if he did.
Unfortunately you're not the first to be with a man like this and you won't be the last.