HELP!! with my 75 Dart

Yeah, it may not make sense as you KNOW the reality, but they truly have no way to attest to the car running good or not before. You just gotta let that go for now.

Running rough after warmup possibly indicates excess richness, and so messing with the carb does make some sense.

If you want to run a quick check of the spark system's strength, then do this:
- Pull the spark wire off of the center tower of the distributor, pull back the boot, and place it so that the metal tip is right at 3/8" from metal (like a valve cover or inner fender)
- Have someone crank the engine and look for a bright spark to jump that gap as the engine cranks.
- If it does, then the spark components look to be good. That still leaves timing and something messed up around the rotor and cap. A timing light is needed and the knowledge of how it works, so yes, you are needing someone competent to run through that.