All sequencing done with PD controlling some external synths and sampler, "mastered" in audacity

Great work only scratched the surface, will give more feedback once I get playing with it a bit more

I was taking a trigger based approach, but is similar to yours, I'll attach for comparison. Shortening a loop length is another way to go about a similar effect

http://www.pdpatchrepo.info/hurleur/bounceybouncey.pd

Vibrato usually refers to minute changes in pitch, which is usually achieved using something like osc~ at a frequency lower than 12Hz to modulate the pitch of another oscillator.
However I'm guessing you're looking to create an effect similar to

?
It can be achieved in a couple of different ways, but since you mention using phasor~ you could use a phasor object to control the rate of a metro object which is triggering the "ball" sound. I can post a quick example if you're stuck

The $0 variable doesn't exist inside message boxes so that'd be why you're having trouble with part 2, you'd need to store $0 somewhere as you instantiate the abstraction and pass it later.
I'm not entirely sure what you're trying to do in the third part though?

Yeah that book is a good starting point, maybe look at prototyping first using MobMuPlat.
As for your drum machines, the sampler.oneshot help file in Pure Data/audio.examples might be a good place to start to make an abstraction for each voice.

Yep absolutely possible, have a look at fiddle~ object, brief explanation here: http://www.pd-tutorial.com/english/ch03s08.html it may not be exactly what you're looking for depending on the type of source material, but you will need some sort of fft analysis