I'd be SO worried in your position op. My dd recently turned 20 and she's had her moments with unsuitable boyfriends too!
It's SO HARD biting your tongue and making nice with the twats!
Dd knew when I didn't like them she knows me too well, but they didn't suss until after the relationship ended.
I've just recently posted on another thread about the dick that stalked her after, thankfully his parents were reasonable sorts and his dad had words with him after I'd let rip at him and also messaged his parents warning we would be taking action if it continued. This was enough to rein him in thank goodness.
My parents (Glaswegian) generally play things cool too, but I had one dodgy one (not much older but aggressive) and my sister had an experience with a chap she went on ONE date with that escalated badly, they had words with these men and put them on notice which thankfully worked.
I think we are too lax and too polite these days.
In the past men who didn't behave correctly were dealt with in their communities, there's a real lack of that now and god knows so often the police are bloody useless (brother is an officer so I'm not anti police per se but on this kinda thing they're pretty hamstrung and too many officers still see "domestics" as a "private affair")
That she isn't being honest with her friend is very worrying, as is the situation with his dc (think it was me asked that)
If he was prevented from seeing his dc because he was a risk to them, chances are police will know about this/there will be records on this.
I would definitely be speaking to the police about your concerns.
I really hope I'm wrong on what I'm thinking is going on here, you need to protect your daughter.
It's EXTREMELY rare that a parent is prevented from seeing their children by authorities, the bar is (imo) far too high on that.
When I was going through my divorce and my ex was playing silly buggers I asked my lawyer about limiting contact for dds sake.
She explained there basically has to be serious physical or sexual abuse for courts to even THINK of terminating parental rights.
She told me of a case she'd had where the father had been released from prison - for raping his child - and she had represented the child to prevent UNSUPERVISED access which some arse of a judge had signed off on! They managed to get it changed but only to supervised at a contact centre. Yep his victim had to make nice with him every other weekend! Apparently he was "reformed" and "entitled to a relationship with his child"
You need to keep a VERY close eye here