Agree, great info by others. Another observation regarding your son's size as it relates to recruiting timing...
You said "He knows that his speed is lacking and should get it up, but he’s had older friends similar to his style of play that run slower and still went to play college ball." and "..very wide frame, bulky".
With that size and frame type at that age for a position player, I believe many RC's will have concern as to which way that will go. The player can make exceptional efforts to assure the size is maximized and become a relatively athletic and agile big guy or the player can continue to battle limitations with his very wide frame from a mobility standpoint. Many D1's will "wait and see" with a guy like this. Many D2's and below will wait for the drop-down opportunity with a guy like this. So, in either case, the timing is likely to be later. Make sure he is putting proper emphasis on assuring he can be as conditioned, athletic and quick as possible with his frame type. Don't allow the "other slower friends played in college" be an excuse not to address this with full commitment.
Even at the HS level, I am battling this issue this year as I do most years. I have more than one big guy with a very good bat but there is only one position at 1b. If I put them at 3b, capable opposing teams will expose us with bunts. If I put them in a corner OF position, their glove and routes may be fine but lack of range allows too many balls to fall that shouldn't.
Edit to add - To confirm what others are saying - we currently have a SS getting D1 attention. This player has every desirable tool to stay at SS at the next level. I can't imagine anyone moving him elsewhere under any circumstances at the college level. The RC that has called the most on him agrees with me yet, he has asked me multiple times about his ability to move to other positions.