Robert, a few random thoughts:
When testing different spin speeds, keep in mind that the amount of vibration may not have a completely linear correlation with the spin speed. If you've ever driven a car with an unbalanced front wheel, you might be familiar with the situation... something to the effect of "car shimmies at 40mph but smoothes out again above 50." I don't know that anyone knows the resonant frequency of a 70's Maytag's spinning mass, or how it changes with different wash loads. But one day you might find the right load and spin speed where, counter to expectation, going SLOWER actually increases the vibration. If you wanted to get fancy, you could put an accelerometer in line with your speed controller, and let it automatically dial down the speed if things get out of hand. But if you have a computer in the mix, you might as well ditch the timer too and start from scratch. It's a slippery slope.
Perhaps related to balance, from your video, it looks like your water level control might be out of adjustment.
Maytag's literature states:
>> "The water level on the Extra-Large setting should register
>> between the bottom of the second row of holes to slightly
>> above the top row of holes in the tub."
In the video, it seems that yours keeps on filling right past that, up until somewhere mid-way up the balance ring? At 1:11 in your video, the water level was so high that it even floated out the fabric softener dispenser cup!
For the loud rapid knocking on the 12th run... Have you verified that an unbalanced tub actually does actuate your lid/unbalance switch?
The switch itself has an adjustment procedure, and yours could be out of calibration. Likewise, having the upper tub cover installed crooked (or perhaps too high or low?) could negatively impact the switch actuation. Even on a non-supercharged Maytag, it should only make unbalance noises briefly before the switch is triggered and shuts the whole machine down. If yours continued knocking until you intervened, I would suspect you have a mechanical or alignment issue that is preventing the unbalance switch from doing it's job... and at 1,000 RPM, I think you would want that switch to be functional!
On the hot rubber smell... Are you sure it's coming from the brake, and not from the belt?
Looks like this will be a great performing machine once the bugs are worked out!
