Your crew nailed all three calls. Regarding the assisting the runner: I bet the "elders" said something about how the guy was going to score no matter what, his linemen had a great push going and the assistance was not the reason he scored. But I say this is what that rule is intended for, good job.
As for the U calling illegal formation, I disagree and so does the NFHS Officials Manual:
UMPIRE
A. After the ball is spotted:
2. Check the following:a. Number of A players
b. Five players numbered 50 through 79 on offensive line
c. Interference with the snap, a false start or encroachment
d. Disconcerting signals by B
e. Note position of ball between inbounds lines
f. Note B's players on the LOS in the FBZ
LINESMEN
A. After ball is spotted:
5. Check the following:d. Minimum of seven offensive players on the LOS