I completely understand, I have Asperger's (which is on the autism spectrum, but not completely disabling) as well, and completely can understand what is going on. I got my license at age 22, living with my wonderful & caring girlfriend, and currently holding a full time job, pay my(our) bills on time, and now can actually hold onto a conversation normally

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My iPhone has been an invaluable tool (for work & play as well)...plus it's a phone.
I suggest you start looking into switching to AT&T (or Verizon) for that matter, if you don't mind me asking what carrier are you currently on right now? Most carriers that I know of including T-Mobile offers a Smart Limit-like feature. And don't forget that you'd also have the Find My Friends app as well, which you can lock down in Settings > General >Restrictions, to keep him from "going off the radar." ....Provided you also have an iOS device that you can load the app and find out where he is.
Another way to keep track of location would be enabling Find My iPhone, but you may be invading his privacy with full access to his iCloud mail, Contacts, and Calendars, because you'd need full access to his iCloud account for this to work out (unless the others here know of another way). With Find My iPhone, you can use any Mac or PC to load up his location (the location of his iPhone), remote lock, wipe, etc as well as send an emergency message (the real usage of Find my iPhone, but it works). You also can get the respective iOS apps, but if you already are going to use an iOS device, you might as well use Find My Friends.
If limiting web browsing is what you also want to do, you definitely want to restrict Safari and get a "safe browser" from the App Store.