I went through a similar journey when I got into photography: I didn't want to go nuts or spend a fortune on gear, I didn't really want to go the video route, I wanted a simple P&S that shot solid micro/macro and ok widefield without having to fuss around much in post processing.
The OM TG-6 (now TG-7) (~$500) is close to perfect for me. I recommend getting the PT-059 housing (~$300) for it, as well as an external flash module (I've really fallen in love with my S&S YS-D3 Duo (~$800)) with fiber RC connector. Finally get a simple tray with arms and a physical shutter trigger (~$150). All in, you're looking at $2K for a good setup that is great for macro/micro and small reef wall scenes. It isn't great at distance shots, but I've gotten some lucky shots.
Now to settings: personally, I found most online setting recommendations -- including Backscatter's -- to be at best worthless and worst frustrating.
Your best bet for settings is to spend the money on a class. My best teacher remains Mickey Charteris at Cocoview resort on Roatan. Pay attention to EVERYTHING he says. When he gives you settings setup instructions for your TG6/7, write them down. During above water practice shooting, pay attention. If he tells you to take 50 photos of a rock, you make that rock a Vogue model. My photographs went from a polite 'that's nice' to 'holy crap, did I take that shot??" in the span of 2 days.
Good luck! You're successfully making your expensive hobby more expensive.
