I hate to rain on your parade but after being with my DH for 14 years I have learned so much. I also now understand a lot of things people tried to tell me before we got married but I shrugged them off. They come from a place of wisdom and love.
I am not a big believer in LDRs. Yes, we all know people who have successfully married due to one. Shoot, I know a friend who married a man she met overseas two weeks after she met him. More than 20 years later they are still happily married with kids.
My concern with LDRs as
@hopeful mentioned, is no matter how much you talk everyday, they allow either one if not both of you to decide what package of yourself you want to present. How much you want to present and when you want to present. If you are in an LDR and you are having a crappy day or you're in a mood or you're out having fun and couldn't be bothered you can just choose not to answer the phone. And then you can claim you were busy, or you missed the calls or whatever. You can blame time difference.
You can muster the "happy you" to present when you talk. And every time you meet in person is like a vacation. After all these years, whenever DH and I are away from home we have the time of our lives. We are super happy, we talk about anything and everything and even the sex is 5000 times better. Because we are able to turn off our every day lives. We are able to live in the moment and have a light, casual, happy relationship. That is why they say married couples should continue to date after marriage.
I have seen my coworker do this. And her boo is only 1.5 hours away from us. She will not answer his calls if they are in a fight or she knows he had a bad day. He will cancel trips to see her for a myriad of reasons. And when they are together it is fun, fun, fun!
DH and I dated in college. It was great because we lived on campus so we really couldn't avoid each other. If we had lived in the same city (instead of campus) if he refused to answer my calls I could show up at his door anytime (another thing I warn women in relationships, my friend is engaged and she can never go to her man's house without calling him first to ask for "permission." Like ever. Never ever.) I respect people's privacy but when were dating I knew for example if I got a call that my mom died I could run to his place, without calling, knock and just go in. Even if I called it would be to see if he was home, not to ask for "permission."
Once you get married you will be together all the time. One of the wisest things I ever had Bey say is marriage forces you to confront your ish/or not hide from your ish or something like that.
I could go on and on. You picked up on this red flag with his friend. How he will ultimately handle this is telling. Watch carefully. And I agree that some things are such huge red flags that you should throw the whole relationship away. DH always says if he had a dollar for every time a woman said, "He is such a great guy except for ________" and then go on to list some really head-scratching major red flag we'd be millionaires.
And I know you won't be as dumb as another co-worker who married a guy in an LDR and they got divorced very fast because they had never decided where they would live after marriage. Neither one of them would budge. (I know, I have a lot of work stories but I have over 1000 co-workers in just my office, let alone our national and international offices).