I was in a situation like that before. First thing I'd advise is couples counseling.

Communication builds trust. He tarnished trust by not communicating where he was, which makes you suspicious of him. Don't ask why it happened, rather, what happened.

When I was in a similar situation, I approached by laughing it off and saying:

• "aww, look at you. You've got a little teeny bopper crushing on you. You must feel really good about having a little girl crush on you like your Justin Bieber" (sort of tease of him for liking that an immature girl is crushing on him, since he's kind of acting like an immature tool himself) or "ooo, shes totally flirting, how cute. She likes what she can't have".

I've also playfully grabbed my man's crouch or hugged/kissed him in front of flirty snacks, got super physical with him, and said "hey baby, I so want to get hot with you right now" "I love my man"... You get the point. Rub your pheromones all over his body and mark that shit yours.

• He's probably thinking: "I have the freedom to do what I want and rebel against your boundaries". What might also work is by telling him " I trust that you won't cheat on me, because I'm secure of myself and frgn sexy as hell. I chose you because of you're sweet, funny, etc. And want a life together (blabla)" but also point "In my family, SO's aren't friends with opposite gender, and that's a value I carry. There's no such thing as a woman and man being friends, it makes things complicated". Don't be afraid to tell him you have traditional values in that sense and that you don't have make friends in the same way. Its ok that you're friendly with his friends, but realistically, same sex friends are the way to go. YOU should be his best and only opposite gender friend.

ultimately, if you really want to see if he's worthy, it may be worthwhile to him that this is something y'all have had issues with before. If he wants to take this relationship seriously, he should treat you with better respect. You should ask him to:

• not bad mouthing about you in front of others (if there's a problem between you two, then resolve it between y'all via communication)

• spend more time together while at an outing

• involve you both together when there's a gathering with Tara

• communicate about any priors with anyone, openly and honestly

• keep each other in the loop of schedules. People that care and love each other will tell their SO their plans

If you do end up going out at a gathering with her, be nice to her, don't let her take him away from you (by hugging, making out, grab his ass, etc). You might surprised by how effective this is, if he truly loves you.
Dive in, engage with her, get between them by getting to know her, her weaknesses, and divert the friendship away from him towards you. Saying things like "awww, you're so cute/adorable" in a way that shows your bf that you see her as a little girl. Maybe even start talking smack about her to him.

I also showered girls with compliments. One time a shank tried hugging my bf, then I got in the middle and responded by playfully saying "no, you come here and love on ME. I'm the pretty half and want the hug!" and with a calm but assertive tone tell her "this is my man, and in our family, a man and woman aren't friends. If you want attention, come and ask for it from ME. I'll be your friend."

When you two fight, she wins. Don't let that happen.

But on the note of him coming home at 3am and not having sex, I don't believe a word he says. If there's suspicion and you're feeling tension, it's a sign of an unhealthy relationship. You could also approach this by saying you need some space and time, consider whether you two are compatible and if the relationship isn't meeting your needs.