I'm laughing at your last post. I make mistakes too when I'm typing here! Sometimes someone's talking to you while you're trying to type or you get distracted by something...and funny things happen.
I do think verbal has to be done in increments of 8 or 10 questions, not fewer, because there is just too much variability by question type, as you noted. So try the Interact method to see whether that works better for you.
Argh, is their software STILL only showing 1 RC question per passage? That's so annoying - we reported this to them when the software first came out a year ago. I would've thought it'd be fixed for the new edition.
Okay, try this: use the software to do just CR and SC, but pick out a passage to do yourself. Partway through the mixed set, pause the software and go do the RC passage out of your book. If it's a shorter passage, do only 3 questions; if it's longer, do 4. Prop the book up vertically so that you have to look up and down (to write), just as you'll have to do on the real test.
Oh, right - and then they don't give the question number, so you can't look it up easily in the book. Okay, this is what I do. I put together sets from the book, and I write down the set of numbers in a random order. Then, I mark all the pages with little sticky notes (the little thin ones, not fat ones) - the sticky note itself touches the problem that I have to do and sticks out beyond the edge of the page, of course. The stickies are numbered (1, 2, 3, ...). Then I number / organize my scrap paper similar to what I'd do for the real test and flip to #1. I pull the sticky off and actually stick it to my paper where I'm working on the first problem (so that I know for sure that this is #1 and I don't get confused about which # is next - I can just look at the last one).
When it's time for the next problem, I just look for the next number up on the sticky and flip to that page. (Remember, the sticky touches the problem you want to do!)
You can use Nav simultanously or do what I do: I use the lap function on the timer on my iphone and then I enter the data into Nav manually when I'm done. (If you do this, don't forget to turn off the screen saver on your phone - or extend it long enough that it doesn't go black before you're done with the next problem.)
Stress in the actual exam and rushing through some questions I believe adversely affected my score.
The exam will always be at least semi-stressful, you will always have timing and mental stamina issues, and you will never be able to do every last question to the best of your ability / time - that's just how the GMAT works. So how can you make decisions that will help you to manage these circumstances? (I will give you some ideas. But you think about it first and tell me what you've come up with before I tell you what I think.