Your son is on the right track, it's even better that he has been doing his PU and SUs with guidance to proper form.
nofodad is 100% correct, form is everything and he will be graded harder when he starts with his battalion. My younger son had the benefit of having an older brother that had been in ROTC 3 years before he started. He was able to watch him and advise him on his form. Your right, most applicants have their PFT given to them by a coach or PE teacher, the guidelines are not always as strict and you can see some pretty high scores.
Both my younger son showed up to school and they gave the APFT to all the cadets looking to contract that Fall, there were three new 4 year scholarship winners in the group, my son was one of them, his PU and SU scores were similar to your son's for the 1 minute PFT. The other two scholarship cadets had much higher PFT, one had listed 75 PU, the other 78, SU numbers were higher as well. At the end of testing my son was the only one of the three that passed the APFT.
When the grader counts both PU and SUs they will only count the ones that meet the regulation. It's not uncommon to hear a count go like this......1,2,3,3,3,3,4,4,5,6,6,6,....as you can see the cadet has basically done 12 PU or SUs and only 6 have counted, if they are not to regulation they just repeat the same number over and over. The cadet put so much energy out for only half the count and they fail to reach the minimum. This is much more common then you might think.
The best advice I can give is to have your son continue to work on both PU and SUs, his current numbers should be just fine for the application but more can never hurt. The biggest thing he can do is to continue to work on his run, get below a 6:00 mile and try and break 13:00 for the two mile. Form does not matter in the run so there is no subjectivity, he can hop on one foot and if he finishes 13:00 or under he gets the max points.
For most, the run is what keeps them from getting a 300 or better, if he has the run down he'll have time to continue to bring up his PU and SUs while keeping the proper form. He seems to be on the right path which is great.