I can almost guarantee that his problem is low pressure and the resulting pinch flats.
You may or may not know that a good habit is to examine the tube and tire of each flat to diagnose the problem.
If there is a glass shard in your tire, it will puncture the replacement. If a spoke head is poking through the rim tape, it will flat the next tube.
We do know hoe is likely not running on proper inflation a lot of the time. And we know he is big. This is a formula for pinch flats.
The flat would look like dashes. May be on one side, but may be in a pair. Are fairly horizontal to the length of the tube.
I say get a solid tire and improve the quality of this guy's life big time. The down-side of solid tires is:
1. they are heavier. Big Dill. A pound each. Big Dill.
2. They are hard to put on. Yes. One and Done.
3. They cost more. Until your $6 tube cost surpasses the $40 solid-tire cost.
4. Worse ride? No - you get these that are at a PSI equivalence that you want. In fact, a limit of these solid tires is that they cannot really get the high PSI some road bikers want; having a lower, cushiony pressure is not a problem. Also, it is well-recognized that the flat-proof tires with a Kevlar layer are a more harsh ride than regular tire, so if you add a tough liner it is apt to give a harsher ride.
--I have done favors for people, including people who may not be college material as they say and have kept the magnitude of the expense to myself, telling them it was not a lot of money, so that my offer to do something such as replace a tire is accepted by the person and their family. As a little favor versus throwing down $100 for a guy's bike. Just do it.