IT'S WORKING !!!
I tried the jumper from the switch "G" to the scratch going to the microcontroller and it worked. Aslo put a bridge with the group since the pad looked dead this time.
It solved the column problem but "<" was still not working.
So, this time, I tried with a long cable and checked EVERY OTHER SWITCH to see if I could find the right group.
And suprise, It wasn't A but F8. I mean, it's completly logic...
I put foam under the PCB after the reassembly (for sound), I think it's going to hold everything together tightly even without glue or flux.
Thank you guys for helping me during the process.
I will hold your community in high regards.