This question is posed in a dropped-off-on-the-island kind of way [i.e. no way back], and it's a really interesting discussion in those terms - but it's probably worth remembering, too, that two healthy, resourceful, well-educated, computer-functional people who own a house can in fact probably find ways to bring in some money if along the way they find they want to or need to.

If you want a trip that doesn't work in your budget, maybe you can do a home exchange. If your house allows, you can rent out a room for a time-limited period.  You can sell some things on eBay, you can consult about something or teach somebody something.  The few people I know who've retired under 60 without all that much money remind me that really wanting to do something at least sometimes is the main thing it takes to do it -- then you sovle your problems, if any as they turn up.

 And actually of course if you hit a snag you can look into a reverse mortgage, though as I am thinking about it that's a later-on-in-life move.