I agree with Bufty on this--how the prose looks proportion-wise isn't as important-wise as it is story-wise. It seems like you're focusing on the bark of the tree instead of looking at the whole forest. Pretty much, if you do a book entirely comprised of action scenes, you'll have a pacing problem even if you use your sentence formula. Pacing is a overall structural issue, not a proportion issue.
In Book #2, I had a huge pacing problem. I just threw action scene and danger scene one right after another into the story. I didn't understand how problematic this was until I read a thriller like that, and, despite all the action scenes, it was completely flat. The "valleys" of pacing, where things slow down give the reader a breather and allows tension and suspense to be built.
Which goes to Book #4, which was my last one. I was having a lot of length problems, so I broke the chapters in half. Instead of 8-10 page chapters, I had 4-5 page chapters. That small change showed up in the synopsis as the story being very choppy. I had to go through and merge two and sometimes three chapters together to eliminate the choppiness.
Using your example of a scene of introspection, if I had one of those in there, I would consider that a "valley" of sorts and think about what needs to happen in the next scene to bring up the excitement level a little so the reader stays interested. Artificial pacing control like the number of sentences or breaking the chapter to control pages may affect pacing in the wrong way because it doesn't take into consideration the flow of the story. It may even actual add additional blocks to to keep the reader from getting involved in the story.