In my experience this stuff can be very hard. Many people are raised very prudish and made to feel "weird" all their lives any time they express an interest in anything other than "normal". If it doesn't happen to them, they see it happen to others so it conditions them to NEVER express interest or condone anything "weird". It gets in there pretty deep too, to the point that they begin feeling self loathing or that THEY are "weird" if they find themselves still interested or turned on by these taboo things.

It can be a massive hurdle to help or encourage someone to get past those internal taboos and some people simply are not able to for various reasons, often social or religious.
All I can suggest is to slowly suggest things you might enjoy, don't "tell" him what he should do, men's delicate egos can't usually withstand being told how to do things in bed after all. Maybe after a particularly enthusiastic session, during the afterglow period, mention "I really liked it when you did...". An example of this for me was way back when my ex wife expressed that she liked when I inadvertently restricted her breathing, this led to her discovering/admitting that she secretly wanted to be choked or engage in other "breath play". Things naturally evolved from there.