Hi Dalilydontspilly,
That is quite the tongue twister 
. Nice amp, and photos. I have seen this before, and you probably are correct the pads are probably ruined. Since the pads are on the bottom of the PCB, unfortunately you would have to pull the entire board out. This is a little bit of work, but not too bad. This means unclipping/unscrewing all the mosfets from the frame (probably getting messy with heat sink paste), taking some hardware off, and sliding the board out from the side. You then should be able to access the pcb traces on the underside, and you will most likely have to solder new connections to them using wire mentioned above or of your choosing. Remember to re-install the heat sink insulators on each mosfet if they are supplied that way. You should be able to line up the connections visually and determine how they are wired. If you can’t get access to the solder trace, you may have to take a thumb tac or something and scrape the paint away from the trace to solder to. Remember we have soldering tools, and soldering blogs on the forum if you need. One is below as an example:
https://forum.digikey.com/t/hand-soldering-guidelines/4032
In case you need extra thermal paste:
Thermal paste 345-1006-ND