For the stripped thread the easiest thing to do would be drill it out and cut a new thread and get a screw to match.
Or get a Helicoil/Time Sert fitted in the same thread.
On the rounded allen key heads,try using a slightly bigger torx socket than the original,hammer it in and go from there.To give it added bite,coat the torx bit end in rough valve grinding paste.
I can do the first one if your local to me(Manchester)or you could post it!