Hey Marc,
Thanks for the reply! I'm glad this is helping so far. I have a few different thoughts on some of the points you made:
First, the end of chapter questions are just a very brief selection of questions that are there to highlight some of the concepts and techniques discussed in each chapter. As I often tell students, the LSAT Bibles are strategy guides, not practice guides or workbooks (which is why we publish a workbook for each Bible, and sell a variety of books with practice questions). So, doing just those questions wasn't really representative of what you had learned or how you would score. That's why all those
self-study plans we publish pair each chapter with a bunch of homework practice—that's the key portion in increasing your score. It would actually have been a bigger surprise if you score had jumped significantly at that point

The good news is that means you have a lot of potential still out there, and getting into a strong practice regime will help your score.
Next, let's move to the use of a timer while practicing. I'm a strong advocate of timing yourself, and the way I'd do it with each practice set is the following (I'll use LR as the example): Do the first 10 questions untimed, then check your answers. If you've done well, move into timing yourself loosely, say 2 minutes per questions. If you haven't done well, do 10 more questions untimed. Keep doing untimed rounds of 10 until you are doing well (at least 8 or 9 out of 10 correct). when you move up to the loosely timed set, use the same procedure. Once you've done well at that level, move up to regular test speed (about 1 minute 25 seconds per question) and keep going until you've mastered it. this may mean you do more than 30 questions, but if so, that's good because it means that was a problem area for you. By the way, with the practice tests, do them as full timed tests. Don't do them untimed or timed loosely; that defeats part of the reason for taking a full test.
Third, let's talk about your score results, and the feedback there. Remember that individual practice tests have variation, and don't test all concepts or question types equally. So you will see some variation in performance there (see my LSAT Casino link in my prior post in this thread). Second, they don't test an overwhelming number of questions of each type, so a single test doesn't really tell us definitively if you are good at a concept or bad. But several test together tell us that, and so as you get more test result, the picture begins to come clearer. For example, on the test you reference, you performed well on Parallel, but not as well on Parallel Flaw. Basically, that's the same question type, so what you really saw was a performance about in the middle. But, if you see 50% on a question type but there are only 2 questions on the test, you can't draw a definite conclusion there (maybe the one question you missed was brutally difficult, for example). So, right now, what I would do is a full review of all topics first, then I would start looking at the accumulation of test results to define what needs the most work. That's the safest route, and you cannot hurt yourself by reviewing everything (and just the review may indicate to you that you aren't comfortable with certain topics).
Please let me know if that helps. Thanks!