Your son sounds like a lot of kids that straddle the D1/D3 threshold. I am not sure what position he plays primarily or what kind of hitter he is against elite pitching or if he even knows, but it sounds like his 85 off the mound is the real spark for the inquiry. While the exit velo. sounds pretty good, based on my observations, there is a LOT more that goes into being projected as a successful hitter at the D1 level than exit velo; I know a multitude of kids who can hit elite high-level pitching 420 feet but cannot help a D1 program defensively or on the bases who are scrambling to find places to play. Hitters have to help a D1 team defensively at that level or they get replaced very quickly. I know for a fact that there are 2016 players out there right now with the size: 6-0 - 200 lb. plus; speed: sub 6.8's; arm strength: 85+ velocity from OF, IF and mound and exit velos in the 90s to play D1, with only JUCO options, having nothing to do with grades or test scores; so there is a lot more to it as a position player than the numbers, which is why the D1 guys generally have to see a position player a who straddles the line a lot before they are convinced.
As far as pitching goes, based on what I have seen, unless right-handed pitchers in their rising senior summer throw consistently in the 85-88 range for multiple innings, show a feel for pitching, with good breaking stuff, it is unusual to draw a D1's attention, even at the lower levels; couple that with the fact that D1 classes at all levels are full for 2016 class and it's hard to imagine being able to generate enough interest that quickly. In my experience there are exceptions, but those are in the cases where a pitcher at the 85 range shows unquestionable projectability and upside from his body type and arm motion - say a very young 6-3 and still thin at 170 lbs or so with lots of whip in the arm and projectable mechanics.
All of that to say, speaking from my own personal experience and that of other families I know who were not as fortunate as ours, if your son is lucky enough to be able to find: (1) a program(s) willing to go to bat for him with admissions; (2) at an elite academic institution(s), (3) that he likes; and (4) any coach who truly loves him, he is very, very lucky. Several of my very talented former players would do back flips for those opportunities. My 2016 was lucky enough to find an elite Top 10 academic school that fit athletically and will be thrilled to hopefully get the chance to take the field in a D3 college baseball game, as any kid of 18 years old who loves the game ought to be. There are countless kids out there right now wishing they had opportunities to play - most of whom will have sadly played their last game. Savor the opportunity your son has earned, take the best one, and enjoy it as much as possible because it is just not that easy to get to where your family has gotten.
Of course, that's just my two cents