From your description:
When I put a volt meter at the battery it reads 9- 10.5 with the tractor running.
I suspect that you have a cutout relay, and the field resistor at the back of the switch(similar to diagram 3).
You didn;t say which resistor is loose,broken, but if it is the field resistor, then that may be causing your problem.
You are using the meter correctly, it sounds like. The voltage reading at the ammeter:
(red to amp meter and black to ground) it reads 1- 4 volts.
sounds a bit funky. The current from the generator passes through the ammeter to teh battery, so you should read(just about) the same voltage at the ammeter as you do at the battery.
You didn't say whether you hooked the battery up positive or negative ground-from your description of teh voltage at the ammeter, it sounds like it may be negative ground. Stock config for a 6V tractor would be positive ground("+" on the battery to frame of tractor). If you swap it, make sure to repolarize the generator(the generator is what you polarize, not the regulator).