1987 Mitsubishi Galant Progressive Failure.

For some time we have had a short circuit which draws about 2.5 amps continually. Not located.
We handle this by disconnecting the battery.
Recently the car stalled several times at slow speed, restarted with one turn of the key. I did manage to get home.
The following day it would not start. There is power; lights, dash, interior & courtesy OK.
Strangely, sitting down on the drivers seat does cause a shut off of lights. This is not a power seat.
I have no idea of a common connection that would affect both starting and the rest. The starter, battery and alternator are recent. Fuses checked, ok. Where do we start looking?
I am in a location where the skill levels are very low. Vin JA3BB46L5HY011101.