The first thing you need to do is an extremely thorough visual inspection
There’s a very good chance you’ll be able to see the problem
here are a few good candidates . . .
plastic radiator tank . . . I’m thinking of the seams
heater hose connections at the firewall . . . sometimes you have to look with a mirror, and you’ll see they’ve been leaking, and/or are still wet. They tend to leak onto #8 ignition coil. It’ll drip down the head and block, and you can see it from underneath
the heater hose coming off of the water pump
I believe your engine has a coolant crossover pipe, at the front. The seals often leak
The intake gasket can’t be the cause of the leak, because there’s no coolant going through the intake on this engine
As for the misfire, it could be something as simple as you need an ignition tuneup, or it could be something as serious as the engine wiring harness is brittle, causing the problem.
I don’t know how serious the misfire is, but if you want some peace of mind, you could perform a compression test. If #5 compression is extremely low, versus the others, then it obviously won’t be cheap and easy fix.
A word to the wise . . . if you do decide to perform an ignition tuneup, replace the plugs, wires, AND the heat shields that go around the end of the wires. There is an extremely good chance you will damage the wires and heat shields during removal, even if you are being very careful.
If the misfire is constant and severe, you can swap coils and see if the misfire moves. Obviously, this diagnostic strategy only works if you have a scanner. If the miss follows the coil, it’s bad. If it stays on #5, more testing is in order.