Ahh wiring.
For the fusible link you really need to replace it. It's probably what protected the whole car going up in smoke given the other damage you've found.
It'd be easiest to find a factory service manual, as I don't know if the other repair manuals will list proper ratings for the fusible links. You can usually find fusible links @ napa but you need to know the size. Toyota measures them in square millimetres. From there it can be converted into AWG and you can buy some. Smaller sizes like 22awg are hard to find but larger sizes like 18, 16, and 14 can be found at napa for around $6 (from memory...)
Also, remember not to solder fusible links, they're crimp only.