Just another great example of how our situations are never one-size-fits-all no matter how many similarities we can draw. In the end, you have to do what makes the most sense for you as an individual. I absolutely understand how DD's allergies put a kink in what would seem normal in this scenario, we're not just talking about a minor sensitivity here - it's actual life & death in terms of decision making where she is concerned.
I think the important thing here Stung, is that you've compiled info from multiple sources & made an educated decision. The next most important thing is remembering to stay flexible for future changes knowing that his attitude & behaviors could flip practically overnight without warning. He may NOT stay happy with this family dynamic forever or he may have a stupendous relapse, impacting family income, etc.
Who knows? Hasn't happened. Can't predict it - but you can be prepared.
A lifetime trip sounds like an amazing idea, as does your DD's school! GREAT update!