Hi Greg,
I gave you some information about what Manhattan GMAT has to offer. I would seriously consider looking at their website to see if their materials might be of interest to you. I think that you are looking for a structured study plan. Well, they do offer that kind of a study plan, but it will cost you a few dollars to be able to get it. If you are into studying on your own, they have a package for that, too. However, from the sound of things at your end, I think that you need something more than just a simple plan with not that much guidance.
Honestly, I would limit your study time to 25 hours a week. How should you study? Well, that also depends on what you think that you need to study in order to feel comfortable with the content material that is tested on the GMAT. And, how would you know what to study if you don't have something to guide you while you are trying to study?
The next thing that might help you figure out what you need to do in order to start improving your situation, is to take a practice test before you do anything else. I would consider purchasing the Manhattan GMAT online test bank for $39. That is a computer adaptive test bank that has 1,000 questions in it, enough to allow you to take 6 tests without repeating questions. I like that idea because when you take a MGMAT CAT, you get complete explanations for each question on the test. That will give you the ability to determine what your strengths and weaknesses are most of all. Then, you can use that as a guide to make your own study plan. Or, if you want, you can sign up for their online course or in person GMAT prep course. Either one of those MGMAT classes are worth every penny of the fee. Those classes and what goes with them, would give you a very useful and complete study plan. In addition, those classes along with the strategies, their problem sets, and supporting material, all were designed primarily to help you to be able to practice the problems in the Official Guide.
Let me know what you think would work for you? By the way, doing problem after problem in the Official Guide or in any other GMAT prep book, with no direction in mind, would not be useful much at all. In the case of a test like the GMAT, having a plan and a purpose for everything that you do, is a very important part of the preparation process.
Greg