I wasn't sure whether you thought so or not, I just thought best to put in that bit of advice anyway regardless.

I don't think you sound harsh or judgemental.
I really don't know, honestly. That depends entirely on the dynamics of your relationship; I don't think anyone can tell you what the best way or time is. If it was me, I would just share
my strange fantasies (I have quite a bunch) and tell him straight out that I think his are fine, or even pretty interesting (if that's not false).