Sadly, I think you are.
The first thing you have to do is accept you do NOT know him.
Secondly, accept he’s NOT a good guy. NO decent man would move in with a woman, and her DD, and marry her without disclosing his background & until he was sure he’d overcome his issues - whatever they were.
Whichever way you look at this, he’s bad news. He’s not who you thought he was. IF he had stopped using at Christmas, why was he still cadging money off his ex up until now? Christmas was only 8 MONTHS ago, it’s a blink of an eye in terms of being an ‘ex addict’ - he’s not getting outside help...he’s either either still using, or there’s more to this.
I wouldn’t say or do anything just yet, but I’d take the day off/call in sick on Tuesday without him knowing. I’d wait until he’d gone to work (go out for a bit if you normally leave first) then I’d gather up all important paperwork & anything of financial value & take it somewhere safe. Given everyone thinks he’s fabulous 🙄 you need to pick where you take your stuff and who you confide in, very carefully.
Then see at least two solicitors, preferably ones who are recommended if possible. Be completely honest with them and then ask them how to best protect yourself and any assets. Then follow their advice - if they give you different advice then post in legal for opinions.
Get a FULL STI check. I’d bet any money he’s still having sex with his ex and god knows who else. Be honest and ask for all possible things tested.