Hi,
In my opinion he is either Thal. Intermedia or was Thal. minor with severe symptoms that required spleenectomy in later life.
You could have gotten a better picture if he had done his blood tests earlier.
An intermedia's Hb hovers around 6-8 g/dl through early life and later might require transfusions which can be delayed or avoided if spleenectomy is done.
A minor's Hb remains quite higher about 8-12g/dl for men and most of the times don't require any special treatment; such are called Thal. Minima or Minors without symptoms.
While there are Thal. Minors who have some complications like lethargy, dizziness and paleness which is a result of very low Hb levels and possibly due to a hyperactive spleen. This can be cured by transfusions or spleenectomy