Y’a, it’s a total pain in the butt. Angled pliers do work best. Good luck with your fillings. Also having the iMac laying down on the workbench helps.

if the water damaged mac doesn’t turn on, the target made with a thunderbolt cable won’t work. You will have to take out the SSD. For your Mac, you will need a specific drive enclosure to match the SSD. You will also need 2 screwdrivers, a torx5 and a pentalobe for opening the bottom case. Check out owc/max sales. They have the enclosure and the screwdriver kit.

https://eshop.macsales.com/item/OWC/MAU3ENVOYPRO/

https://eshop.macsales.com/item/OWC/TOOLKITMBA/

If the drive is encrypted, when it mounts on the functioning mac, you will get a prompt for the user name and password for the main account of your partner’s laptop.

You may be able order the cable off eBay. Some of the cables have a connector on each end which means you can replace it. If you damaged the connector on the logic board side you are a bit more screwed as that will mean a board replacement. Don’t spend money on new screws, just use needle nose pliers to hold the screw while you screw it in.