hugging? Very yes!
kissing? Yes.
smut? Depends, but yes!
fighting? He's terrible at it, but go for it.
powers? Yes.
killing? Please no.

fourth walling? Actually, I encourage all of you millennials to voice your distress at having to learn his theorem.
thread hopping? Ask first.
back dating? Overall yes, but depends on the thread.
cross canon? My favorite.
cross medium? Don't mind at all.