Strength training: the Four Percent Solution? Or what other formula for increasing weight?

The low reps, low sets with weights are working for my chronic-pain-bad muscles! At least, I can tolerate the exercises and added a rep each, and so here we are. I even have actual DOMS today instead of the nerve and spasm pain, which is so amazing I can't describe it :) Thank y'all so much for your answers to how minimal I could go on reps and sets.

Now I need to know how to progress it. I don't want to be doing a lot of reps or even sets because of my particular back/neck problem.

Don't worry about my actual back, but please give me general feedback on this progression regarding weight and reps, with strength and nice, slow progression as the goal:

http://www.strengthsensei.com/the-four-percent-solution-for-fast-strength-gains/

Not slow enough??? These particular muscles are so weak and the lifts so isolated that I'm still using water bottles, so no worries about finding small enough plates or anything here, lol. I like the idea of raising the weight by a percentage and that's easy to do with volume of H2O. Thanks!

(I'm only able to hit them 3x in 13 days right now, btw. Unfortunately, the rest days are still pretty damned necessary, but I'm hoping to get to 2x a week within maybe a month or two. Let's call it twice a week for discussing the Four Percent Solution or other program since that's easiest, though.)