Assuming for a second he reaches all of those projections....
yes you sign him, w/o hesitation.
The durability means that you'll need a backup on the bench and have to use the backup for a decent chunk of games, however you can usually find a good defensive SS with a decent enough bat to hit 8th or 9th at little cost over the time frame that it takes to develop that guy.
However, on the flip side once the playoffs start, you'll likely have the best overall SS in your world, a huge assest. If you give him proper rest during the regular season, you won't have to worry about him being less than 100% when playing him every day in the playoffs with all of the off days. If you're paying attention you can rest him vs right handers in games where you're playing a rebuilding franchise. Sitting him 40-50 games a year will cost you a few wins, but build up the franchise around him and you should be able to land one of the 6 playoff spots then have the availability of the best overall SS when it counts the most.
Now, the question is, can he really hit those projections. Is he an 18 year old that is relatively close to all those numbers an realistically w/n reach, or is he a 21 year old that is never going to come anywhere close to those projections and is more likely to be what he is today when he is 27 than anywhere close to what those projections say. If those projections are realistic, I'm guessing he's asking for $7-$8.5 mil. I believe $10 mil is the top asking price, which I've seen a grand total of 1 time.