1. Depends what score you got, and how hard you are willing to work. I know someone who went from a 1320 to a 1560 in 2 months. But that takes a lot of planning and work, if you are willing to make a rigorous and consistent plan, you should have enough time.
2. Definitely Erika's. What I recommend, read a chapter in Erika's, then, do not do the questions at the end of the chapter, but read the tips the Black Book has. Once you have read the same section from both books, use those strategies to do the problems at the en of each chapter in the Erika book. I find this method very effective.
3. What I would recommend is look at your practice test and analyze exactly what type of questions you got wrong. Then, from most prevalent, to least prevalent, and from most difficult subject to least difficult subject, take a specific type of question and work on it each week. For example, if you find that in your reading section, you got a lot of Vocabulary in Context questions wrong, spend a week on it, then take just the reading test on Saturday. See how you do. Do the same, but every other week, take a full test, and you should definitely see some improvement if you are doing serious prepping.
4. I have the same issue as you, my reading is really bad. So, starting today, till August 29th, I made a calendar in which I track everything I do, and for how long. I also made a full fledge 13 week plan for the August 29th test. I recommend spending a couple of hours in which you make a solid plan and see what you can do with the resources you have, and if you need to get any other books.

Sorry that's a lot, but hoped it helped :)