Are these valid points my boyfriend is bisexual?

I believe I am a fairly non judgemental girlfriend. My boyfriend loves his own ass and loves me to spank/squeeze it during sex which I like to do as anything that turns him on, turns me on. As a female however this is a bit of a blow to my femininty as no man should pay more attention to his own ass than a girl. Whilst yes, he does compliment mine, generally speaking the attention is focused on his. Excuse me if I sound weird myself however I find it odd that my boyfriend loves me to give him hand/head and even loves to masturbate when he is in doggy position. Basically on knees, leaning forward with ass in the air. He loves me to go from behind. He also loves squatting which he finds pleasurable. He finds it easiest to cum in those positions and of course during sex which is usually him on top but finds it hard to cum laying down on his back if I give him hand/head. He has told me that masturbating in other positions is not effective and if that he just squats down, he cums very quickly. I've seen it before and he even flexes his feet so he's literally just balancing on his toes. When I have asked before, he tries to give me unreasonable explanations such as "gravity" which makes me even more puzzled.

The issue is that it is interfering with our sex life. When we first met, he couldn't cum. It was only till after many tries of doing everything to please him, that he could cum inside yet he was still somewhat squatting, just penetrating this time. It was very frustrating as sometimes I would give him oral for 40 minutes or so, obviously enjoying it but no ejaculation. He put it down to masturbation, porn and performance anxiety. It was only one night where he was able to cum, that was inside me and somewhat squatting. I have mentioned to him that in order for him to be able to cum and not be desensitised, he needs to slowly try other positions masturbating so his body also gets used to it. He has agreed to do this yet still mentions he has tried other positions however it is not that effective. He believes just refraining from masturbation itself will help, yet I disagree because even if he does that like he has done other times, he still will only be able to ejaculate in me in particular positions such as missionary where he is somewhat still "squatting"

Do you find this quite odd? Why would one continue to masturbate like that and not find other positions effective as he claims? Is my suggestion the correct suggestion?

Edit - last night we were on the phone and I asked him to refresh my memory about a gay story he had whilst away on holiday that he told me months ago about a gay male hitting on him. He first told me he ignored him yet last night he said something different. He told me that the gay man at the party was telling my boyfriend he gave off a bi sexual vibe and asked if he's ever been with men and that it is only a matter of time. Again, I asked if he IS bisexual and he said "no, end of story" I told him that I would be disappointed if I found out he was lying. He said I will never find out as he isn't bisexual. He mentioned I could ask his friends and that they would laugh at it as they believe he is homophobic. We then were speaking about different masturbating techniques and I said to search on google as plenty of advice and different forms will come up, he mentioned he could look at male solo's. I asked why he would do that as it sounded homosexual and he said "yes actually that does sound very wrong. Just to be able to see how it's properly done" do straight men ever watch male porn or at least watched it ever and stopped?

 

Thank you. In fact, he does not like anal play and has told me that. He has said he does not mind me touching though. Obviously as this is off putting for me that he masturbates like this, makes me question a lot of things and interferes with our sex life, when is there a point where we are just simply sexually incompatible and time to think twice about the relationship as well?