I think that the "funny looking tab" he's referring to is the tang on the left dropout. It's function is to guide the axle into the dropout. The derailer hanger serves the same purpose on the other side. It's seen mostly on earlier frames, but my '74 has one. It works very well.

The thing in your picture is an axle stop. It should be all the way back for best shifting and there should be one on each side.

You definitely don't have 700c tubulars on 27" tubular wheels since 27" tubular wheels don't exist. You need to reglue them before you ride the bike. I actually prefer the Tufo tape to tubular glue, but that's your choice. I wouldn't change to clinchers, but that's also your choice. I think I can change tubulars faster than I can repair clinchers.