Hi,
There isn't one fuse that will shut everything down and then slowly power it back. Either you have a dead battery or it's a ground issue. If you take a look at the attached pic, it indicated where one of the main grounds is located near the rear seat. Check it.
Also, take a volt meter and check the battery both with nothing on and then with the headlights on. See if it drops. Check continuity between the battery negative and a place under the hood where you can find a good place to ground the multi meter. I'm curious how much resistance there is. Also, and I don't know what all has been done, make sure none of the fuses are bad in the rear fuse box.
Let me know what you find.
Joe
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Sunday, February 16th, 2020 AT 7:03 PM