Sorry I didn't get back to you on this:

?#1. I'm not a fan of cartridge filters, but a lot of people seem to like the Pentair Clean & Clear line.

?#2. With a 2 speed, you can toggle lo/hi OR you can just run on low all the time, except when cleaning or backwashing.

?#3. Filter spruce up: Open, check, and probably, add sand.

?#5. Replacing the motor on a Super Pump is an acceptable option AND that motor has a manual toggle (I think!)

?#6. Dunno about those. CarlD likes his; the ones I've seen sucked . . . and not in a good way.