I need major relationship/friendship advice...

Okay, first off. Brace yourself, this is gonna be a long story, but I'm gonna make it as brief as I can.

I really need an outside perspective of everything.

My bf and I have been together for almost 6 years now, about a month away. For the past year we were discussing having a threesome, it wasn't until I believe October (2019) that we actually took the step to meet people on tinder and try it out. For adding a female into the mix, we used tinder. For adding a male into the mix, we decided to ask my one of my guy friends (I'm a really shy person and I wanted to do it with someone that I knew well enough that I wouldn't be completely awkward and shy, my social anxiety at times can be crippling to me, I didn't care about the female part because that was mainly for my bf, but I wanted to be completely comfortable with the guy one). We did the girl thing (December 2019), I wasn't a fan, yet of course he keeps asking for another threesome with a female, even though he knows I wouldn't want that because it went so bad the first time. 2 boundaries I had set were broken during it, one was broken by me giving into it, the other was him "forgetting the boundary". Next, we've been trying to set up a day to have a threesome with my friend and it just always seems to get cancelled or rescheduled for a wackload of reasons, literally felt like it was just not meant to happen. My guy friend and I exchanged nudes during this time to keep the interest there and to tease. My bf knew about it and was all for it. Come January (keep in mind from the time my guy friend said yes, up until Jan. It had been 2-3 months), I started to lose interest in the male threesome, not just with my friend, but also just in general. I knew my bf found it hot, so I tried to play-up my interest since then. Come to a couple days ago, I asked my bf if I can go meet my guy friend for a coffee just to catch up. He said no. My friend and I always take separate vehicles to a public destination and always during lunch time. Never in the evening, never getting "drinks" as in alcoholic drink or dinner drinks. Him and I don't see each other in a romantic interest kind of way, he's legit the most kind, chill dude that would NEVER overstep boundaries and I HAVE NEVER and WILL NEVER put myself in a situation where I would cheat and that is 100% not the type of person I am. My current bf of 6 years, emotionally cheated on me 3 years ago and I never tried to get with or talk with other guys with ill intentions in mind. But anywaaays. My boyfriend no longer is okay with my friend and I having a friendship. I understand that crossing the boundary of inviting him into our sex lives would be touchy, but I didn't think he'd make me completely cut him out of my life after everything... Trust me, I see my bf's side of things and I understand him feeling uncomfortable, but it's like he all of a sudden doesn't trust me or my friend to be able to push the sexual stuff aside in order to be friends. I know it sounds like bs, but I'm not kidding my friend and I are chill af and can move on with our friendship like nothing happened, plus lately him and I only ever meet up once ever 3-6 months. It's really hard because now my bf has basically given me an ultimatum of "it's him or me", which makes me FURIOUS because I don't want a relationship where I need to be presented with ultimatums. In NO WAY do I have feelings for my friend, but he is important to me in some way and I am a firm believer that people are put into my life for a reason and I can literally feel that my friend is suppose to be in my life for some reason, but I haven't figured out why yet. I'm in a tough spot because they are both important to me but in different ways and for different reasons, but my bf thinks that I'm choosing my friend over him just because I don't want to cut this friend out of my life.

If you made it this far, I really just want to know what I should do. Should I just give in and just make my bf happy even though it'll make me miserable and I'll probably hold a slight grudge for cutting someone important to me out of my life?? Or should I stand my ground and fight for my right to have this friend, a friend that I completely trust to never cross boundaries and that I would never cross boundaries with, but risk losing my bf either completely or in a way that we might not be the same?? I'm seriously torn... I know how messed up this all sounds and that it should be an easy answer of choosing my bf over anyone, but idk it just doesn't feel like the right decision to me... Help!!!!!!

Thank you in advance! Also, try not to be too mean to me, I'm genuinely confused and mentally and emotionally screwed up over this and just need some wisdom and some advice.