Correct, it is the x10 device with the problem, they have problems with electronic devices that make more noise. But even with it being the X10 device problem, other ballasts do not seem to make the same "noise" and do not experience the same problem.
It may. There is a known issue with the icecap ballasts causing interference with X10 devices. I would run the icecap with a direct connect or get one of those add on's that decrease the interference. I think they have them on the neptune site.
You should have it drilled for a closed loop IMO. Sump to tank flow is only for the purpose of feeding a skimmer and a place to put a heater. Whatever the feed of your skimmer is + maybe 50 gph for some water to go through to feed macro if you have that in the sump as well.
Flow should come...
2 years is one of the longest times I've ever heard of someone having one. They are best left in the ocean as you can't provide food for them. They slowly die of malnutrition over about just a year. Occationally someone will have one for more so consider yourself lucky.
I would drill a few of holes for an overflow that runs the length of the back to maximize surface water removal ans well as some feed holes for closed loop with a manifold style return on the closed loop. If only I could go back.
Same with me, about 3-4 g/day. Mine is mostly due to a stock tank sump and 2 open top frag tanks. That and my canopy isn't finished so the ends are open. Procrastination.
I do my water changes on the weekend and immediatly mix up new. So a week. I have done it faster but only when there is an emergency or ?? If I need it faster I throw a mag 9.5 in the 32 gallon brute container instead of the maxijet. Always with an air pump though. I think the shortest time...
You need very little flow through the sump itself. Really only enough to feed the skimmer. Most of your flow should come from closed loop/powerheads/etc. How much of that is only limited by your substrate.
They get thier food from the water column. You will see them hanging one leg off the glass many times to get food. 2 years with a starfish is great (except brittle and serpents). That is really the reason so many are against having them in captivity. They basically slowly starve to death.