Meant to ping you to the above as well. :~)
I get the impression from the boy that he is still undecided. Can you bear it for another day? Can you play a radio or a CD on an endless loop near the crate so he can't hear Mom?
If he doesn't settle down in another 24 hours, I would go ahead and neuter him and turn him back out to Mom. But WATCH him because he will smell funny and she may reject him.
The mounting behavior is normal for kittens, it doesn't mean anything sexual until he is more mature (I assume his little testicles haven't descended yet.)