I don't know what too do or what it can be I'm lost...
This won't cure your problem but may give you some insight, while the battery is up, disconnect your negative (-) clamp and see if it sparks when touching the post. If you have a draw, it will spark. Then the fun starts in seeing what it is. Sometimes it can be the security system.
1989 Blue LX Hatchback
2001 Red SVT Cobra Convertible (Phoenix)
2002 Black/Red GT (Ginger)
2011 Red Candy Metallic V6 (Manfred)
2016 Magnetic Metallic GT (Susie II)