I did the IB diploma program and enjoyed it thoroughly! It gave me an opportunity to branch out and pursue a truly multidisciplinary set of studies. I was able to accelerate and cover upper year undergrad material and got early university placement. It was basically just a transplanted undergrad.
While the program has a loose curriculum, a lot can be customized to suit the individual student or institution. I was fortunate in that I was basically given the freedom to study any supplementary topics I wanted. My success was, I believe, the result of a good fit between the school and myself.
If your son is getting worn down, I think it would be worth reevaluating the resources available to him. Are the teachers staggering deadlines across courses? What level of one-to-one instruction is available? Is he informed about readings in advance? Given latitude for self-study? My studies really took off when lecture attendance was optional.
I don't believe a student--particularly a HG one like your son--should be unhappy. My nose tells me he's receiving an inappropriate style of instruction.
IMO, the program is ill suited to students who have a splinter interest, or even students pursuing a pure science career due to university prerequisite requirements. Some of my friends aiming for med school were getting burnt out carrying extra courses to meet admissions requirements, and people who had difficulty with large reading volumes were getting bogged down like your son. These were high achieving gifted students, too.
My first major was economics, so I had fewer constraints. I was able to play on varsity teams and do about 20 hours of extra curricular activities during the week. I'm embarrassed to admit that, as a terrible procrastinator, Sunday night was when I cracked the books.
I'm sorry I can't comment personally on the health considerations.
Hope that helps!
