Hey Kitten....that was a really good point.
Wondering......I think looking into Y's motivation is a good next step. I too think that you really know what you should do, but are fighting with yourself over it. I wouldn't sacrifice my integrity either......somehow it would just feel tainted from the get-go. (and as a stab in the dark), if you are considering taking up with somebody that has the ability to do ....whatever it is that is making you think so hard......may also open you up, to be subject to some of the same down the road?
Them being with you won't change who they are......but you'll be changing who you are to be with them....knowing what you know.
(talking in riddles is hard....lol)