This could be good. I am not all that familiar with Magoosh or Total GMAT Math. So I am not in a great position to really evaluate much of your plan.
I do have a couple of comments.
One is that part of the reason for taking practice tests is to figure out what you need to work on and how you stand. That information can be valuable to have on an ongoing basis. So one thing that jumps out at me is that by only taking one practice test in three months you will not be getting an optimal amount of information, or an optimal amount of practice in taking the test.
For one thing, there are many different areas of quant, and some show up more on the test than others do. How will you get a feel for that, and for what you need to work on, without having experienced the test?
So while I agree with waiting, and not burning a GMAT Prep test unnecessarily, I think you should consider taking more practice tests and taking them sooner in that first three months. If you don't want to get down, maybe you need to find a method of staying up that's better than avoiding the test. You mentioned meditation. (Yay) So maybe you are familiar with working with your mind and emotions. I am sure you can come up with other ways of staying positive about your prospects. For one thing, the truth is that anyone can learn to rock this test. So getting down or discouraged never makes sense.
On another note, SC can take a while to get better at. So if you need work, there, maybe you should do more on that in those first three months too, or maybe that's included in the Magoosh work you mentioned.
Generally I advocate taking a video game like approach to learning about and taking the test. For one thing, GMAT quant is more of a reasoning game than a math test. That's less of a comment on your plan than it is something to keep in mind as you prepare.
Does doing the Economist program ten hours a day make sense? That's an interesting idea that actually I kind of like, even if ten hours might be a lot for you, though it does sound like fun to me. When I was preparing I would do questions until I could barely think straight, and then do some more, often at like 1 AM. So maybe you will be that way too. At the same time, that program has a certain way of looking at things. So does making that the focus of your entire power week make sense? I guess you will find out.
So I guess your plan sounds pretty good as far as I can say given my lack of familiarity with some of the materials, but I tend to feel that maybe you would be better off making the process more of an iterative feedback loop than what you have is.
