Don't know exactly your answers, but can give you some info to I think help.
Many inverters are mounted to the ceiling of one of the basement bays, probably close to the house batteries (so the cable run is short). Look for a big white box, with thick cables that go to the batteries.
I haven't seen that remote before, but Magnum has all of their manuals on their website. You may have to dig around there to find it. My remote is an ARC-50, but doesn't look like yours at all.
http://www.magnum-dimensions.com/
If you can't find it, give them a call. They've got a good help desk.