How do you officiate this play

[Football101]

Down and distance does not matter with this play.
Team A has a running play that has three reverses behind the line of the scrimmage, The play takes forever. At the snap number 72 blocks a member of team b beyond the expanded neutral zone, then retreats back to the Line of scrimmage. Then we have a forward pass that is completed beyond the Line of scrimmage I was taught that the ineligible down field was when the pass was thrown, but reading 7-5-12, I guess I was wrong. Is there anything in the football fundamentals that would not make this a foul.  What makes this a very hard foul to officiate as being a wing official, I do not want to throw my flag for the ineligible down field until the pass, just encase there is not foul and we have to pick up the flag.

any suggestions from others how they deal with that kind of play.

[CalhounLJ]

Down and distance does not matter with this play.
Team A has a running play that has three reverses behind the line of the scrimmage, The play takes forever. At the snap number 72 blocks a member of team b beyond the expanded neutral zone, then retreats back to the LOS. I was taught that the ineligible down field was when the pass was thrown, but reading 7-5-12, I guess I was wrong. Is there anything in the football fundamentals that would not make this a foul.  What makes this a very hard foul to officiate as being a wing official, I do not want to throw my flag for the ineligible down field until the pass, just encase their is not foul and we have to pickup the flag.

any suggestions from others how they deal with that kind of play.

I guess the first thing we need to do is fix your situation to include a forward pass beyond the line of scrimmage. Because you describe it as a running play with three reverses behind the line of scrimmage...

[Football101]

Fixed, Thanks for catching that mistake, it does clear it up some

[KWH]

The applicable Rule is 7-5-12
The applicable Casebook play is 7.5.12 SITUATION A including the COMMENT

[bossman72]

The ineligible player can't be down field AT ANY TIME before the pass is thrown (which eventually crosses the LOS).

[NVFOA_Ump]

One of the problems here is the NFHS code is black & white in that once the lineman is downfield it's s foul if A later throws a forward pass that crosses.  The defense knows that and plays run at that point.  The rule could be changed but IMHO that gives A an advantage that isn't needed.