My opinion, take a step back , with all the " maybe's " and " hope so's " you are setting your son up for another setback.
My first question would be why do you want to showcase him if he is not 100% ready? It's great to work with the MLB guy, and I have never worked with one yet who did not promise great results. I mean what do you want him to say?
It goes without saying that the injuries sat him back, but showcasing without being on top of your game is a huge mistake.
If he was 86-87 healthy and pitching 84 injuried, I do not see 90+ in a few weeks. And trying to get him there quickly is a mistake.
The grades are good but not earth shattering , its good that he does have them , because right now without them would not be good.
So lets say by showcase time he is sitting 86-88 as a RHP that has good control and good off speed pitches. As a RHP I would try and find a good Juco with a good coach that has a history of getting guys to the next level. This will give him more time to re-coop and hone his skills and get playing time.
I cannot see a RHP 6'2 170 player even at 90, coming off injury , squeezing into a D1 program having any kind of impact his freshman year.
Now one exception would be if he really , really wants to attend this school for academics. But I did not hear that.
My 2013 was a very good HS pitcher, a late bloomer, good grades and good desire and work ethic. We knew he was not D1 coming out of HS. He went Juco and logged innings. He then transferred to a better Juco and he filled out, got stronger. He is now going to a mid level D1 next year. He is a RHP at 6'3 200.... and he does not hit 90 87-89 but... has pin point control and many off speed pitches in the zone. , basically he is hard to barrel up and knows how to get outs.
If he had barley gotten into a D1 program out of HS he would not have gotten the chance to grow , improve and get exp...
You have plenty of time, there is more than one way to get to your goal, but don't push him into a failure, or another injury.
Also, if you are trying to get a walk on spot at a D1 more than likely you will be disappointed.... Get healthy, go to a school where he can play, have success at that level and go from there.
I'm a little concerned that we are not getting a 100% complete story here. Where would he have gone to school without baseball? With his grades and scores, he would be in line to attend a really nice school without baseball. Has he applied to any schools yet?
If baseball is the reason nothing has occurred yet, IMHO the advise above is a real good way to go. It gives your son time to heal and develop. Best of luck!