My 1998 200sx shuts down after about 5 miles

sounds like a fuel problem, how many miles on vehicle? as a quick fix it would be worth using a fuel addative , you haven't said if petrol or diesel, if petrol get addative that covers the catalytic converter ,having a blocked exhaust system can cause engine to stall also get the OBD codes read as this will tell you what if any sensors/switch's are faulty

I noticed you did a lot in trying to find the problem but I noticed that you never ran the fault codes to check for where the problem was. Run the fault codes and tell us what they were.

Could it be your clutch? It could be slipping., Revving higher than it should when changing gear? Put it in a higher gear when driving at a slow speed like 20 if it is revving when you put your foot to the floor but the speed is not matching it. The clutch could be on its way out.

Is the check engine light on while you're cranking the engine?

Many cars have the cooling fan on a thermostat or time delay, to allow it to run for a short period of time after the engine turns off, to cool the engine off. You may have just never noticed it before. So I wouldn't worry about that.
Your real problem is the blowing fuses, apparently you have a short somewhere in your wiring. Putting in bigger and bigger fuses is a great way to set fire to your wiring harness. It's possible that the wire is pinched or chafed somewhere, and perhaps when you hit a bump just right, it touches and shorts.
You may have to take this to the Chevy dealer or a GOOD independent shop to have them chase it down. Unless someone out there knows exactly what this is, it could be a tough one to find.

Sounds like an engine sensor problem (could be one of several) - start with an error code (DTC) check with a good code reader and follow up if there are any.

well i never warm my car up in the mornings its all down to how you drive it, if you flog the nuts off it its going to were out a lot faster if cold but drive it with some cear do oil changes on it often and it will last at least you another 100,000 miles as for the rattles
all motors do that at 100,000 miles lets fase it how much would you rattle if you had walked that far?
just drive it with a bit f tlc and it will get you there

Well 145K is alot of miles, catera's are not that reliable especially after 100K. It sounds like you could have multiple issues but take it to a mechanic asap before it becomes unfixable.

try replacing your EGR Valve, or your Oxygen Sensor

Sounds like one of the fancy heaters. They have circuit boards that can go bad. don-ohio