2 live ball fouls ?
 

During a punt in a game tonight, there was a block in the back by R and during the tackle there was a facemask aganist the new D 15 yarder. do these offset or do you mark off both?

Assuming that the block in the back was a PSK foul R may keep the ball by declining K's foul. If they accept the K foul the two fouls now become a double foul & offset. You go back to the previous spot & down. Give both signals & wave them off, Replay the down.

Canadian Ruling
 

CANADIAN RULING:

If the BIB was before R gained possession, go up 5 yards from Point Possession was gained, 1D/10.

If the BIB was after R gained possession, go up 5 yards from Point Ball Held at time of BIB, 1D/10.

So you "net out" the penalty yardage?

Extra Point foul
 

On a extra point, def has a PF penality. Is this assessed on the kickoff?

Yes. The 10 yards for the BIB and the 15 yards for the FM are balanced at the Point of Application of the first foul. This gives the 5-yard difference.

Assuming the try was successful, yes.

Actually, if they kicked the extra point, K can take the point off the board, accept the yard and a half and then go for two OR they can take the point and assess it at the succeeding spot, which will either be the subsequent KO or into OT.