Bigger issues

Hey ladies,

I need some advice. I’m 20 yrs old and my newly boyfriend is 21. We’ve been dating for a few days but have known each other for 3 months. I currently live in California and he’s in Arizona, but there are some extensive circumstances and blah blah blah i’m moving back BUT NOT for him. I was moving back before we were going to date. Anyways, he is my first boyfriend and I’m his fourth maybe. None of his were too serious besides one and she broke up with him. Now, he has got to honestly be the most perfect boyfriend. He does everything a hallmark movie man would do. Seriously. I don’t know how I got so lucky. Here’s where things get messy. His best friend is a girl. They’ve known each other for 6 yrs and I’ve met her and we get along enough... well they went out to a bar last night with some other friends while I went out with some girlfriends. He comes home and tells me that some guy kissed her (she has a boyfriend of 6+ years) and that he threatened to kill the guy. Which okay, is a little extreme but I get he was drunk and being protective. I get that, BUT I asked him if he and her have ever done anything and he tells me they hooked up ONCE when they went out of country for a college trip 2 years ago. She told him that she was on a break with her boyfriend. Alright, so she’s checking out as sketchy in my book and raising flags and he has told me if I’m not comfortable with them hanging out AS often that they were both okay with that as he is “100% committed to me” but idk, as I’ve never been in a relationship before I was having enough anxiety as is, but this just really sets up foundation for disaster... We talked about it and about all my concerns and he’s reassured me that he would never do anything to jeopardize our relationship, but how do I go about this? Any advice?