have power till turn key on, then everything goes completly dead

Hello, it's very clear that you either have a battery issue, a cabling issue and / or a connectivity issue among all components. I would personally be focusing on the cables and connections. If moving the positive cable makes a difference, that's a major clue. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.