penalty mark placement

[bniu]

okay, I've got a few scenarios below that I am a bit confused on, and I'd like to know where to go on this:

Team A has the ball at their 25 yard line, 2nd down and 10:

Team A rushes to the 38 yard line, holding at the 36 yard line by a downfield blocker. I enforce the penalty from the 36, taking it back to the 26, what do I have? First and 10 at the 26?

let's say they now have the ball at their 25 yard line, 2nd and 20
Team A rushes to the 42 yard line, holding at the 40 yard line, enforce 10 yards from the 40, taking it back to the 30, now what do I have? 2nd and 15? (wouldn't they have just gained 5 yards from doing that with no loss of down?)


thanks in advance for any help...

and btw, does anyone know how the NFL assigns the pro bowl referees? I know the super bowl is the best of the best at each position...but not sure about pro bowl...