Sounds great. Good info. You said your spark looked weak, so I'm leaning toward a coil issue.
Remove the distributor cap and spin the engine over, make sure the rotor spins.
Check for oil or metal shavings inside the distributor housing. If any are present, replace the distributor assembly.
Now lets test the coil. Turn the ignition switch on, distributor cap off. Check for 12 volts at the black/yellow wire that fastens to the coil with the small phillips head screw. If you have around 12 volts, next
Turn the ignition switch off. Use an ohmmeter and check the resistance between the 2 screw terminals on the coil (detach the wires first), it should be between .63-.77 ohms
Check the resistance between the "a" terminal (the one the black/yellow wire was attached to) and the tip of the coil where the spark would come out. It should be between 12.8 -19.2 ohms.
If either of these are out of spec, replace the coil.
If you don't have access to an ohmmeter, remove the coil and look for burn marks in the side. They will arc through usually, when they go bad. I have replaced several of them in the past year. If you need anything else, let me know. Keep this question open until we know for sure your problem is repaired. Thank you for allowing me to assist you!