Remote terminal for battery. 1993
 

Is the red terminal on the fuse block, next to drivers side fenderwell, designed/okay to use tk jump start the car?
Or is it just for charging?

Those are the big fuses, I wouldn't jump there. Yes, it is a pain in the ass to clamp the C4 battery's terminals, but ensure you have the right jump cables to get a perfect grip.

I got a post extender and it works great. Take the short post out and installed longer one.

FYI/PSA, if you install a extender for the battery post, use something to rough it up so it has good contact with the battery.
Mine was polished and it was not making good contact and I had intermittent starting issues. Took it out, put the factory short one in, and fired right now issues for 2 days so far..