Sometimes fantasies are best left as fantasies and while sharing them can create deeper intimacy, acting them out often backfires. There’s a reason people have fantasy lives and it’s to keep their real lives safe. The fantasies are a safe way to explore thoughts and feelings without risking hurt feelings among their loved ones and themselves.
I think it’s great that you and your boyfriend are exploring your innermost thoughts and fantasies, but your boyfriend sounds more conventional than you, and I think if you push him too far you’re going to run the risk of ruining the relationship. Skim this forum for other similar situations from readers and you’ll see that more often than not, a threesome results in a relationship break up.
What you’ve omitted in your post is YOUR feelings about sex, and I”m not sure if you’re looking for more kink and excitement in your own sex life or if you’re just trying super hard to take care of your boyfriend by ferreting out his fantasies and then making them come true by enacting them with him. If it’s the latter, consider backing off and keeping your mutual fantasy lives something you talk about, but tiptoe and baby step into. If it’s the former, consider how important your sexual exploration is when weighed against the value of a relationship with this guy without that exploration. I think you may be incompatible sexually, and the ball’s in your court as to whether you are willing to veer more towards vanilla sex or push the envelope and risk losing this guy because the kink is too uncomfortable for him.