Getting into grad school with a low gpa
It sounds to me as if you definitely have a chance, though the GPA is somewhat low. 

The fact that you became better over time with regard to GPA is a very good sign. You may want to calculate your GPA by year so you can cite some figures if asked. Be prepared to explain why your GPA was low, or at least what you did to improve it. While interviewing, do not be late for an interview with faculty - study the campus maps and be sure to let any prior meetings to end soon enough to give you ample time to get to your next meeting! Being late may give professors time to look at your transcript and possibly ask some awkward questions that you otherwise likely need not worry much about if you have already gotten to this stage in the application process. Not to mention being late is not a good thing in general.

Make sure you can secure some good letters of recommendation from your research projects. This is absolutely critical.

Hopefully, the job you get over the next year is also somewhat research related. If it is not too late, I would try to find such a job. Also, I don't know if it will suit you, but if you can find such a job, then you may even want to keep it longer than a year depending on how things go. If you can finish a good project, that will boost your chances even more.

Finally, I think your plan for the subject GREs may be alright, if it does not interfere too much with my suggestions above. Taking tests is not a big part of most PhD programs, and even those where it is, only a few of the most selective programs require the subject GREs last I checked (which was a while ago).