Welcome to the forum.
My plan is this: enroll in a terminal MS program in order to be brought up to speed, and then from there, once I have the research experience, referrals, and overall credentials to be taken seriously, apply to the more prestigious Ph.D. programs to which I will have ideally gained access. Of course, this will not be this easy, but I am willing to spend a considerable amount of time and energy making this work.
this is a great approach to get into a p.h.d school with your current background. master's degree will help you a lot to gain qualifications for phd admission.
Here is where I am now: I have taken and done reasonably well on the General GRE. I would now like to take the Physics Subject GRE. As someone who hasn't taken a physics course in about half a decade, do you have any advice on how to best prepare? I am well-versed in the ETS website's skeleton for study. My hypothetical solution is to buy respectable textbooks on each of the subjects and begin to toil away. I suppose my question is, would you suggest any reading in particular that can help me along my way? Or is there a better way to go about doing what I plan to do? Something tells me Wikipedia won't suffice. In addition, I have read horrendous reviews of all one-stop-shop Physics GRE texts, so I do not even consider this to be an option at this point.
you are pretty much on the right track. in my opinion, you might take the physics gre test more than once. to get into a MS program you usually don't need to have pgre scores but given your situation, you shall try to take this test and a get a score to show them that you are not a total stranger to physics. if you search this forum, there are several topics about the preparation techniques for beginners. what I have found as the most helpful advice is this:
Holiday, resnick fundamental of physics is the best textbook for getting prepared for the test. after that you have the griffiths books for E&M and quantum and your favorite textbook of classical mechanics (e.g. Marion or Taylor). 5 released actual pgre tests by ETS are your best resource to know the level of the test and level of your knowledge. most people would say these are enough materials to ace the test. you may not get a stellar score in the first try, but that will hopefully get you into a good MS program and during your master's you can definitely improve you score. as I said, if you search you will find more comments with more details about the steps that I mentioned and other different approaches.
Also, it should be said that I am comfortable with calculus, and have come to understand that I will need to learn linear algebra. Is there any suggested reading in this arena, and is there any more math that I'll need to learn in order to do well enough to gain entry to a Physics MS program?
if you are comfortable reading the textbooks I named earlier then you wouldn't have any problems in terms of math background for MS program. see this topic for applicant with background other than physics viewtopic.php?f=3&t=2909
and this viewforum.php?f=18
on how they got prepared.