Sir, you just saved my day. I've quickly compiled and flashed a new firmware with qmk and the board is alive again. Now I will try to solder the remaining switches!
Thanks a bunch! I was on dismay!
Glad I could help.
As the quickest of tips on soldering switches:
1. hold the soldering tip on the switch pin AND touching the pad (the metal ring around the switch hole in the pcb)
2. touch the solder wire to any of the surfaces in contact with the tip, preferably the soldering iron tip.
3. after a small portion gets melted on the tip or the pad, take the wire away and WAIT for that melted solder to be "sucked" in the hole (that's when you know the solder has connected the switch pin and the pcb pad).
4. Remove the hot tip at that point.
In case your switches do not work in the future, it will probably be due to this process being done improperly and because of the vibration from usage, the ball of solder that is improperly connecting the pin to the pcb has shifted position.