Well it was drawing nearly half of the full load on it's own, but when wired correctly lowered the draw and never had a problem after that.

As for the alarm: depends where they've put the power and earth. If there's a few wires going to the battery they may have added the alarm on to one of those, so disconnecting this wire will stop the alarm (as well as whatever else is on it). Or could have ran a stand-alone wire to mingle in wih the others and be disguised?? Just guessing.