How many questions do you guess on typically?

I would never use any company test to draw inferences about how the real scoring algorithm works. Company tests are not using the real scoring algorithm. So I would never look at those percentile changes and derive a guessing strategy from them. That strategy would not be likely to work on the real GMAT.

While it does seem that pacing is an important issue for you, I also wouldn't use a company test to judge just how important that issue is. Real GMAT questions tend to be clearly worded, with simple setups, and with simple calculations. That is not always true of company questions, and some test takers who have pacing issues on unofficial tests find their pacing issues substantially less severe or non-existent on the real thing.

As you study Quant, you should find you get faster at recognizing how to get started on problems, and at carrying out solutions. If, after preparing thoroughly, you have trouble solving official questions within 2 minutes (OG questions, say - once you've reviewed all the content, be sure to do timed practice), then it may be that you're using inefficient methods, and you may need to learn new ones.

It is true on adaptive tests that most test takers need to guess quite often. Once the test has a fairly good idea of your level, it will be trying to give you questions that you only know how to answer properly about half the time. So you should expect to guess quite a lot, and you shouldn't be concerned at all about doing that - it's normal, and it's actually what the test expects you to do on hard questions. The single most important principle to bear in mind is this: it does not hurt you much at all to guess at a hard question. But it can hurt you a lot to guess at an easy one. So you ideally want to avoid guessing at many randomly chosen questions at the end, because if any of those are easy questions, that could be a minor disaster.

Instead, if you know pacing will be a problem, you should be making quick decisions about 30 seconds into a question: do I see a way to answer this? If you really don't have any path to a solution quickly, and you're well-prepared, it's very likely the question is difficult, and a guess won't matter too much. You should take those opportunities to guess, to save time for questions you'll be able to answer. If you do see a path to a solution, invest your time to get an answer, even when that might take a bit more than 2 minutes.

That advice is for the Quant section. It's a bit harder to pick good spots to guess on Verbal, because it takes longer to recognize hard questions. But you should be using GMATPrep to discover if pacing is an issue at all in Verbal. If so, you'll probably want to guess at CR questions in the middle/end of the test, since CR questions take longer than SC, and longer than RC questions once you've invested time in a passage. RC questions will also often be easier than your CR questions, so are riskier to guess at.