I don't think the fetish means as much as their character. If he is trustworthy to you and if you think he will cheat. All long term sexual relationships usually require compromises from both parties. I would be grateful he is not into some more off the wall.
My wife recently started like bondage stuff and it's not something I like much. I know how important gratification is like that so I started making an effort. I watch more videos on that stuff to learn and just made an effort to adapt for her.
I think if what he likes is something you just can't handle then you might be better ending things. His desire for the fetish won't just go away. If it's something that you are a little scared by then let him know why you're a little apprehensive about trying it. If you are willing to compromise then he should be too and not try to force something new like that in you at full force. If you worked though it you could develop a much deeper sexual relationship together.
That being said, his specific fetish seems like it would make him more likely to cheat. Sexual fixation comes and goes. He might not even be into that in a year or two and he might even just work it out of his system until he get bored with it.
You seem pretty competent and level headed. Approach with caution and trust your gut