And it works great as long as I'm on the same network. But if I'm not on my main network the PC struggles to load GNOME and eventually crashes. What do?
The OS will wait until the mount is successful with these settings, which is why GNOME doesn't load. Try adding nofail to your options. It should continue with the boot process if you are out of the network with that option set. (https://wiki.archlinux.org/title/Fstab#External_devices)
Adding nofail will most likely fix this. However switching from fstab mounts to systemd mounts could be cleaner as you would be able to create a systemd target that gets activated whenever you're on your main network and then trigger a mount of the share / unmount when you leave.
I have had bad luck in the past where my drive would not spin up at boot for some reason. I end up modifying the fstab file with a live boot USB and then start the system with revised FSTAB.
Just my 2 cents that would help in case of a dead lock situation.