Your brake lights outside stuck are on? That is actuated by a grey switch mounted near brake pedal. Those are picky and you have to adjust them correctly. So it’s either that or the switch is not even mounted. It could be hanging there.So I've had a parastic draw on the truck for about 1.5 years now. My truck never sat long so it was never really a big deal until now. I'm not sure if it's worse or it's just because it's sitting longer now. I have a 1.3-1.5 amp draw. When I disconnect fuse 51 it goes away to below 50 miliamps which is what is supposed to be at from what I've read. I've narrowed it down, I THINK, to the cluster. The reason being I take the three plugs out for the cluster and the amp draw drops from that 1.3-1.5 amps to the less than 50 miliamps. I plugged it back in, amp draw went back up. Unplugged radio, didn't change. Yeats ago I sent the cluster to circuit board medics, several times it had a couple issues with it not being calibrated right, and I put in led bulbs in it. Some of them never really worked or would work if you hit a bump and shook them. But with the fuse 51 pulled the cluster and overhead still work including the backlighting on the cluster (I think), but the radio would not work at all and neither would my Smarty touch in my OBD2 port. So, is it actually the cluster or could it be somewhere else? I'm having issues with the remote not working either, but that could be an issue with door wiring or the aftermarket remote start I'm not sure. The E brake light is also staying on and the brake lights are all staying on all the time too including the 3rd brake light. Which I've read could be the master cylinder or the reservoir switch, tried 3 nothing changed. Did the 4th gen hydroboost with 4th gen master, didn't have issue before it so I think it just may be a bad resivour??
As for power draw, unplug smarty and radio and see if it stops. Those smarty touches draw a bit while parked.
Also I recommend unplug/remove aftermarket remote start for testing. That may be the problem too.