Sorry to hear about your husband's injuries.

I don't have any experience with the same injury. However I'd imagine in most cases first class seats will be your best bet. Be careful with bulkheads, some actually have worse leg room depending on the aircraft, airline, and how it's arranged. Seatguru.com, while not always totally correct, can be a good place to research legroom and compare between carriers.

I'd also think that minimizing any connections would help, as would avoiding regional jets which, even in first class, can have less room than a mainline jet.

What airport would be your specific destination in PA?