Piston::
Slight movement of the piston is normal, alot means it's piston/bore time. It sounds like it may be alot.
Rod/crank::
1mm movement on the rod/crank is OK, I think the rod/crank is fine from what you've explained.
Carb::
Any carb cleaner should work fine. To remove the needle seat there is a tiny phillips head screw. Only screw in there, should be a easy find.
I don't mess with that brass tube under the jet.