First and foremost, there's no DFU mode on a A1708 Mac, thus whatever you try you won't get into DFU. If the board works, you should be able to getting into recovery mode at startup, regardless if the battery is disconnected.
From your description you seem to have a full array of different issues that would seem to head straight to liquid damage or some kind of high level damage. Remove the board, inspect with microscope and reassess to start with.