I don't know anything about your specific tractor but I do have a 1973 Ford 2000, 3 cylinder gas tractor. So, based on my experience with my tractor, here are a couple of questions/things to consider.
1. Have you checked the timing on the engine with a timing light? My I&T Manual has a pretty detailed description of setting the timing at different engine speeds and with the vacuum advance connected or disconnected.
2. It's virtually impossible to work inside the distributor on my engine because it is located directly below the intake manifold and is too close to the manifold to work inside the distributor. I always pull the distributor to do any ignition tune-ups. Did you pull the distributor? It's real easy to put it back in while it's one tooth off from where it needs to be.
3. On my tractor, the only fool proof way to insure the engine is on the compression stroke and is at TDC is to manually roll the engine over and observe the markings on the flywheel to see the zero degrees mark on the flywheel. Again, on my tractor, the only way to reliably roll the engine is to use a screwdriver in the teeth on the flywheel. The fan shroud and location of the radiator make it impossible to get a wrench on the crankshaft nut on the front the engine. The problem with getting a screwdriver into the flywheel is that you can't access it without pulling the starter.
Any carburetor problems you might be having are an entirely different issue, so, good luck with your troubleshooting.
Tom in TN