After months of problems it seems I fixed at least the worst of them (the cranking problem) without knowing but by following feelings. I thought one of the cables didn’t have enough diameter to allow 600+A while cranking to pass through and it seems that could have been the problem. Now it also only uses about 450A during startup. Maybe the heat and therefore the resistance buildup in that cable was too high… We will see in the next weeks on how it develops. One main short circuit remains for fixing, but at least I got rid of all the bridged fuses 🙂