I too was suffering the same issue, I ended up adding a relay to the ODB2 cable in effect disconnecting the main power line between the ODB2 cable and the hub/tablet. IT does slow the drain but still not enough if you don't drive daily. Next step is hard wiring
@Dairusire should have come to the Drag day, dont need powersteering to drive in a line 😎
Glad its not all bad though, sounds like its going good and a PS pump is easy compared to the drama you have behind you.