OK, this is more for Ralph's edification, because we've already been through this (NCAA).
When any fumble goes OOB, unless affected by something else, the play clock is 40 seconds, and starts automatically when the ball becomes dead OOB.
For any forward fumble OOB (and Team A will continue to snap the ball), the game clock stops until the ball is spotted and officials are in position, when the R is to sound his whistle and signal for the game clock to start (including inside 2 minutes in the 2nd/4th periods). Yes, if the ball spotting/officials-in-place process takes us to less than 25 on the play clock, by official interpretation (A.R. 3-2-4-I) we need to pump the play clock to 25 and it should start automatically, without interrupting the game clock.)
(Now, that's the way it is SUPPOSED to be for any OOB condition, except inside 2-mins in the 2nd/4th periods. But TV has pressured the NCAA to have the R re-start the game clock almost as soon as it is stopped. So, you will see the R wind within 2-3 seconds after the ball goes OOB (in possession or loose) - LONG before the ball is spotted. When we first got the current timing rule, Redding issued written instruction (I still have that bulletin) that the R is to sound his whistle with his signal. But the 'cool kids' decided not to sound their whistles. So, today, the vast majority just wind within seconds of stopping the game clock. I always gave my whistle a short tweet with my signal.)
[Having said that, by UIL Exception for high school football in Texas, we do NOT re-start the game clock after out of bounds stoppages (in possession or loose, except forward fumbles OOB). So, there is your precedent, if y'all choose to keep the game clock stopped.]
Regarding the Momentum Exception, following possession of the ball in the field of play, a fumble by the defending team from their own end zone that goes OB (in the field of play or end zone) is, in fact, returned to the spot of the fumble in the end zone, and, officially, the ball is dead at that spot. If impetus is with the defending team, that's a safety. If impetus is by the opponent (via forward pass interception, backward pass interception/recovery, legal kick reception/recovery, fumble reception/recovery), the Momentum Exception applies, which gives the ball to the defending team at the spot where possession was gained in the field of play.
