Given the offer, it sounds like the package is OK for a single person.
Has got an offer confirmation in writing or is he looking to apply?
If he has not progressed at his current employment after x years, he’s either not hugely motivated to develop professionally or they regard him as middling player. Either way he’s not an immediate candidate for this posting otherwise the offer would be made to fit his profile &/or he’d be actively coached for progression.
i second the suggestion that you pass the baton to him to work out & prove the case for the logistics as a reality check, before considering throwing his hat in the ring or agreeing to a contract if there one.
He sounds stuck & frustrated, maybe feeling that life has passed him by.
The past couple of years have warped many people’s routines & plans leaving a wake of discomfort & discontent.This is a reasonable position to be in & start working towards change.
Having his support through your most difficult of times showing you love & loyalty is very important, but that does not mean that you owe him unquestioning agreement to what he proposes. As he could see you through the hard turbulent waters to a safer surer shore, you can do the same for him by helping towards a sustainable & fulfilling way of earning a living?
Working with him on a personal & development plan based here working with animals offers him something real & your support for this confirms the goodwill between you. A good start would be to look for local volunteering opportunities, so he could start now, be enthused, appreciated & energised. This is an effective counter to his daily grind.
You have much to look forward to with new opportunities & you must not put this aside for your sense of obligation & that debt. He helped you through the hard times so that you can live your life well.
If he is dogmatic & determined about the overseas offer & takes it, then he should go alone as there is not enough in the pay pot for you & your family to live well.
Hopefully you can find a good way forward together here.