Good luck Jacob, you will get it in the end.
Would check the rom jumpers as Nino suggested. Have you tried the board with only U6, U9, U11 installed? Have you also tried the -35 chips in the M-100 to confirm these are alright? Would also buzz the following out (from
www.pinrepair.com) if you haven't already, as some of the tracks between U6 and U11 passthrough U7.
I had a similar board, I repaired. It wasn't quite as bad as yours but someone had tried to remove the corrosion, lifted most of the tracks under U8 and then drilled out the hole to each pin to a larger size.
U8 pin 1 (A3) - U7 pin 20, U6 pin 5
U8 pin 2 (A2) - U7 pin 21, U6 pin 6
U8 pin 3 (A1) - U7 pin 22, U6 pin 7, U11 pin 35
U8 pin 4 (A0) - U7 pin 23, U6 pin 8, U11 pin 36
U8 pin 5 (A5) - U7 pin 18, U6 pin 3
U8 pin 6 (A6) - U7 pin 17, U6 pin 2
U8 pin 7 (A7) - U7 pin 15, U6 pin 1, U11 pin 24
U8 pin 8 - Ground
U8 pin 9 (D10)*- U7 pin 6, U6 pin 14, U11 pin 29
U8 pin 10 (D00)*- U7 pin 6, U6 pin 14, U11 pin 29
U8 pin 11 (D11)@- U7 pin 7, U6 pin 15, U11 pin 28
(* U8 pins 9&10 shorted together)
(@ U8 pins 11&12 shorted together)
U8 pin 12 (D01)@- U7 pin 7, U6 pin 15, U11 pin 28
U8 pin 13 (D12)*- U7 pin 8, U6 pin 16, U11 pin 27
U8 pin 14 (D02)*- U7 pin 8, U6 pin 16, U11 pin 27
U8 pin 15 (D13)#- U7 pin 9, U6 pin 17, U11 pin 26
U8 pin 16 (D03)#- U7 pin 9, U6 pin 17, U11 pin 26
U8 pin 17 (CE2) - Q5 rt upper leg, U9 pin 40, U11 pin 34
U8 pin 18 (OD) - U18 pin 6
U8 pin 19 (CE1) - U17 pin 8
U8 pin 20 (R/W) - U7 pin 16, U11 pin 21, U9 pin 34, U18 pin 7
U8 pin 21 (A4) - U7 pin 19, U6 pin 4, U11 pin 22
U8 pin 22 (Vcc) - C13 left leg, R12 upper leg, CR5 lower leg
(@ U8 pins 11&12 shorted together)
(* U8 pins 13&14 shorted together)
(# U8 pins 15&16 shorted together)
