Thanks for everyone's input, so to summaries from my original 2 questions I'm getting that
1) If the O linemen's hand goes on the facemask, no strike and not continuous, 10 yards illegal use of the hands as per 9.3.3. However if it's not seen as deliberate, eg the hand slides up as the D player is trying the shed the block, or as per the exception in the rule the D player squats, ducks or submarines, then no foul. This foul only applies to O linemen.
If the contact to the facemask is with force, ie a strike, or the contact is continuous, PF 15 yards, and this goes for both the O and D linemen.
2) Running backs have an exception under 9-1-8 so no PF for continuos contact, and 9.3.3 only applies to "A teammate of the ball carrier or a passer" so no illegal use of hands either
So he can put his hand on the helmet/facemask and then push the defender away with it or he can fend him off at arms length by the helmet/facemask.
If however as the defender is coming in for the tackle the runner extends/swings his arm and contacts the helmet/facemask with force then that's a foul as per 9-1-2a, due to the force of the action making it striking.