Your strength seems to be sky-rocketing. Which makes sense, since you are basically training in the "strength & power" range. I might try your style of clustering, it certainly looks to be very effective at strength gains.
Whats your advice regarding how to program the volume for these cluster sets, and when to increase the loads?
Well first off, not only am I the strongest I've ever been, I'm also the biggest I've ever been. My upper arms are now sitting pretty at 17.5, which I'm pretty happy with, although I'm also (paradoxically) disappointed because I know the majority of that is biceps increase and I need to find more work for triceps. Forearms are the biggest they've been, legs are back up to where they were when I was training them more regularly but I'm most happy with the back development (all over) and upper traps.
Regarding how the clusters and max-stim work:
-If I can do 5 reps with it the upper load, it's generally time to bump.
-Somewhere in the 8-15 rep range per exercise, depending on the load (closer to 2-3RM, vs closer to 5RM) and whether it's the first exercise hitting that body part.
-I bump the upper load during a workout if I can do the 4th rep of the cluster comfortably.
-Obviously there's a bit of intuition involved for loads.
-Rest periods are 3 minutes as a minimum, realistically. You know, 3-4mins. Frankly, I'd be surprised if anyone could do 3RM clusters a minute or two apart.
-Failure is not a part of my training philosophy; all going back to the CNS.
-Form is important. You don't dick around with near-max compounds. And when you forget/get ahead of yourself, you break a rib ... oh no, wait, that was me
-Max-stim: hard to say exactly what load to use. You'll find you can probably do 15 or so max-stim reps with an M-time of around 30s or so at your 3-5RM (probably varies a bit depending on the exercise, technique and relative strength). If you start spacing that M-time out longer, the workout takes a bit longer but you're going to get stronger and bigger as well. I don't think 1RM is what you want to be using for max-stim. But up to 3RM ish-range is fine. 5RM is also fine, and there's no reason it would work 'less well', except you'll probably need a few more reps to achieve the same results. If we were to graph progression over an extended period of time, you'll progress faster if you expose yourself to higher loads sooner rather than later.
-EAT. But, having said that, if you're cutting, I still find this style of lifting to work well. You aren't inducing intense energy needs during the work-out and you can stretch rest times a little if you're tired. Caffeine is also awesome, obviously. I've had to go off it for a while for medical reasons, which sucks, but I'm doing fine w/creatine all the same.
-Courtesy of Totez, I dropped deads to once in every three upper sessions. They're CNS heavy and I need/prefer extra time to recover.
I use load as the mechanism for inducing stimulus for hypertrophy. Obviously any successful program factors this in, but many trainees will use extra volume as a mechanism for inducing hypertrophy before/rather than progressing the load. My decision to do this is partially based on preserving the CNS. I find volume to be a greater inhibitor of recovery than load is. Additionally, and just as importantly, it's well established that progressive load (an increase in threshold load, if you like) is required to continue inducing the stimulus needed for hypertrophy.
What we're aiming for is microdamage, and load progresses past adaptations (of which I'm fairly sure are significantly connective tissue adaptations more so than muscular) rather than volume. That isn't to say there isn't a place for volume. But I promise I'm gaining more doing 12-15 reps and 3-5RM range than the guy doing 5x5 and 85% of 5RM. And as we know, strength and size go hand-in-hand. It's not a linear correlation, but it IS a correlation. Hell, I think we can say is causal effect at this stage, we just don't understand it as well as we'd like (yet).