I am not sure what answers you want with the questions, but I am thinking that something is not right. If you/he thinks he is going to develop and wants to play D1 ball then he should be going to a JC. D1's will be picking up 2015 pitchers in particular, later in the season and then he would be available. A full ride to a D2 is great (actually much better than great) if it is the right school, it is a disaster if it is not. Frankly what is more important than $$ is the overall "fit", which there have been tons of threads here recently about this with early transfers, dropping out, etc
What was his PG rating at the PG events ? 84 is below average for a RHP going to D1's. All the stats you mentioned don't mean a thing to a college coach, it is "stuff", mechanics and projectability. Also who has rated his "3 above average pitches". I kind of doubt that someone with a below average velo has an above average slider or curve for example. (college level not HS) I have seen many very very successful HS pitchers who could not make it in college who threw lots of breaking pitches that HS players could not hit. Put them in a strong college situation and they would be destroyed.
So it really gets down to: Is he in the right program/school/situation. If not then find something that is right for him. If it is right, then why worry about being under recruited?
I am responding to your post since I just had a discussion with my son while he is back from college on break about him making the right school choice, he too had a "full ride" (combination academic/athletic) to the wrong school for a whole bunch of reasons and we discussed what might have happened if he went there. He turned it down and will be graduating in 4 years with a very employable degree and he had a good baseball experience (not perfect by any stretch of the imagination) He is also 6'4" and was also in the 84-86 range during his Jr year of HS. He jumped up a bit in Velo during the fall of his Sr year and started getting a bunch of late D1 interest, and ended up not picking his final school until May 1st of his Sr year.(D3) That said he was in discussions with a number of programs who said they would come out and watch him during the HS season, which a bunch did. (this was 4 years ago) If he has programs following him then this is something to consider.
Similar to Chefmike, my son's program played a D1 (probably top 50-100 type) over the fall and the first 6 pitchers they faced were all sitting well above 90. My son's program had 2 sitting well above 90 and 6 of the 7 they pitched all touched 90.
So after all of this, if he really is not satisfied with his offer then don't take it, if he is, then why worry. There still is plenty of time, particularly for a late bloomer who is tall, but don't base your/his decision on HS related numbers comparisons.
Good Luck.