I got a new main battery and backup battery and installed both.
Received my previously loved ECU for $150 online and already opened it. The part of the case I removed got bent but I will bend it back or look for a new one later.
Here are the pics:
https://ibb.co/Ms9Jzk9
https://ibb.co/Yj6JYH9
I should receive my KESS tomorrow and looking forward to causing some trouble!