Its the JBJ ATO I think.
It's either the float switch or the Aqua Lifter. It's easy to test....plug the Aqua Lifter directly into an 110 outlet and see if it pumps. That will tell you if it's the Lifter of the switch. If the Aqua Lifter is making noise and not pumping...it's most likely the rubber diaphrams which can be purchased separately.
As far as heaters, I like Eheim Jagers. They are longer then most others, so just make sure you can fit it in the area you wish to put it.
Agreed. Also helps with O2 levels. And you know you will put corals in eventually so don't kid yourself.You don't need as much as in a reef, but you still need good flow to prevent junk building up on your rocks etc. I would keep the same flow you did for your reef personally.