Regarding #4 & #5
PG has said multiple times that they ask that you do NOT mention RT artists in credits.
Neither PG nor the artists want that to occur, but I don't recall the word 'prohibit' being mentioned.
Do the right thing and honor the request, it's the easiest safest route.

If you think artist 'X' being in the credits is what is going to make people like your song, well ..

I do not work here, but the benefits are still awesome
Make your sound your own!