What you need is to map out your study schedule. A FT job is a obstacle you will need to account for but since your testing in August, you have plenty of time, even if you study part time. I would recommend you minimize your work hours to <25 / week if you can, starting 2-4 weeks out from your test date.
Next Step offers a few study schedules you can check out in our forum
here but the important thing is ORGANIZATION. The less time you have to devote to studying the more efficient/effective it needs to be. Start with a diagnostic exam (both MCAT and just science) to see what areas you are strong/weak in and to diagnose which aspects of the MCAT give you the most trouble (aside from the science of it).
Next, decide on your resources. Quantity =/= quality. Do not just buy 3 sets of books or 20 FL exams. Peruse the available books online or in a local store and then see which type suits your learning style best. You can also mix and match as some companies like NextStep and others, allow you to buy individual books.
Aside from content, you'll need plenty of MCAT practice, and I don't just mean Full length exams. you will need practice passages, section practice, and small quizzes to slowly build your knowledge base and MCAT thinking skills. There are several Strategy and Practice books available, make sure they are for the new MCAT, lots of stuff (like EK 101 verbal, 1001 Bio, 1001 Chem...etc...) was designed for the old exam. If possible, purchase a set of content books that also have lots of MCAT practice Qs in them (EK, Next Step, TPR do this well, Kaplan, not as much) to save $ and make your study more efficient.
Buy all the AAMC materials. You will get 2 practice tests, the section bank, a sample test (1/2 length), and the AAMC questions packs (the least new of their materials but still useful).
You can always sign up for a course to get lots of exams (TPR, Kaplan) or some companies sell them separately (EK, NextStep). I would not buy more than 6-10 exams, and even if you do buy 10 a few of them will be used as smaller practice (section, 1/2 section, passage pairs) sessions.
prioritize and triage your time from now till August. How many hours can you devote, each day, to your MCAT. What time of day? Do not study exhausted. About 10-15 hours is sufficient if you have > 4 months to go, which you do. Set long term goals such as:
When will you be done with your content review
What subjects will you study and in what order?
When will you begin half section or section tests as part of your prep
When will you have nothing left to do but FL exams and review (ideally the last 2-4 weeks of your prep).
Study in places where you can focus, and that there are NO distractions. 3 well-used study hours are worth 8 in a busy Starbucks or with friends in a library or conference room if you are not focused.
You may have to cut some things out of your life for a while (same goes for when your a med student, I promise you). Schedule some down time each week, but long weekends, frequent nights out, will have to take a backseat for now. Believe me, your family/friends will forgive you.
Hope this helps, good luck!