"There is no IFT application to a PF shot against infantry in a building. *If* hit, then follow on shots in that fire phase ignore the TEM."
I agree, but there is still a benefit against the target infantry. We should apply the same TH mechanics - the TEM is applied once to either the TH roll or the IFT resolution. PF would apply it to the TH roll because they have 0 FP value, unlike the other SCWs.
The 37.47 rule is a compromise between ensuring a faust is used for its intended purpose - destroying AFVs and not used against infantry. To 'encourage' the player to shoot at armor, they reduced the effect on infantry to no wood building TEM. In actuality, they were often carried by German AFV crews and used in close defense against infantry. ASL gives them 16 FP, IIRC but they also remove the counters and abstract them with an availability DR.
But the ASL rule is better answered by David, who has a much better understanding.