IMO the danger is very small, but using socket savers will usually fix the problem. And protect the tube sockets as well.

That seems highly unusual. Can you post a picture of one of the tube sockets? In my experience with a lot of tube amps the screws are spaced wide enough that they aren't a problem except with very rare (extra wide base) tubes. But a standard socket saver, like a standard tube base, will always fit inside the screws. There can be a problem with some adapters, but not with a "normal" tube.

Interesting. IMO at this point you have 3 options. 1) Send the picture to Steve and see what he thinks. 2) Make small notches in the tubes with a Dremel/file/xacto. You aren't going to damage it if they are just big enough for the screw head. 3) Live with it. If it were me I'd go with 3, but your call. Good luck in any event.