Welcome back Commie Panda! Congrats on your score. I know it is not as high as you were hoping, but a 164 is still great.
So, as you can see, my main concern is that I won't have much study material, as I realize taking preptests is the best way to study.
I would just like to say that just taking preptests is NOT necessarily the best way to study. In fact in can even be quite helpful to review questions you have seen before. A lot of times when we take a test or a section, we are worried about just getting it right or getting it done quickly. When you take another look at the same question, you can worry more about why the wrong answers are wrong and why the right answer is correct. On games, for example, I will often redo the same game over and over again. Each time I may learn something new about it that I hadn't seen the previous time. This deeper understanding allows me to see the patterns more quickly and efficiently when I look at a new game that I hadn't seen before.
So the concern about having used the materials may not be as much of a concern as you think. I have been looking at LSAT so long that I have probably looked at every question multiple times. I have most of them memorized at this point, but I still feel there is value in looking at them again when I am studying.
You also mentioned it has been six months since you have really looked at this stuff. It is also possible that you won't remember much of what you did before. That said, some of the other sources you mentioned could still be valuable. The superprep and the older LSATs still could provide you additional material that you haven't looked at. I would avoid any non-real LSAT type material that is generally sold commercially in the bookstores.
The other concern is whether I have enough time between now and Sept 30 to get back all the knowledge I have (it's been 6 months so maybe not too long) and to also improve on that so I can be confident into the test Sept 30.
It is sort of like riding a bike. Granted, I never liked that expression because after I could drive, I pretty much stopped riding a bike. I got on one five years later, and was actually quite wobbly. Granted, with just a little bit of refresher, I was able to ride the bike qutie smoothly again. And in that sense, the LSAT really is like riding a bike. You may feel wobbly when you first start up again, but within a week or so it should feel like it did before the February exam. Then you still have over a month to solidify your score in the higher 160s/170s range before you take the exam again.