Vancouver Island might work.
-Not bonkers expensive, if you stay away from Victoria. The forestry industry has been dying for the last 30 years, you can buy a place in one of those little north-island towns for nothing these days.
-Reasonably well developed, for most definitions of "reasonable". Not third world anyway; the RCMP, Medicare, and the BC school system are about as good as you will find anywhere.
-Place with nice fit women who are kind to American men? Your mileage may vary, a lot. Being nice, fit, and kind yourself will go a long way.
-Place where I can make a nice living in the Diving/Hospitality field? There's a few other operators around, and I think God's Pocket is for sale right now. Seems to me there's room for growth in the industry, especially now that we're down to zero remaining liveaboards.
-Best diving in the world, if you're willing to be a cold water diver. The water is rich and there's a lot to see, but that's a really big "if" for most folks; it's different from the Caribbean experience. Cold, low vis, strong current, bad weather: your customers need to be a bit tougher and more adventurous, not to mention better trained and equipped. Those customers do exist and need to dive with someone, why not you?