There are a lot of folks in the nontrad forum (under premed) who are ex-lawyers, might want to look around there.
(1) Do medical schools factor in grades in graduate programs like law school into the applicant's GPA?
Nope. You have to report your law school GPA, but it's not a big factor. The critical number is your cumulative undergrad GPA, including your postbac. 3.6 is average for med school.
(2) How long realistically will it take for me to finish medical school--I am guessing at 2 years for a post-bac program, 1 gap year to apply to medical school, and then 4 years of medical school.
Yep, then residency, which is 3 years on the primary care end and 8-12 years on the neurosurg end. If you haven't taken any science, and/or if you haven't done much math, then 2 years is more realistic than the 1 year that you may see advertised for postbacs.
(3) Are there any grants or scholarships out there to help with the costs of getting a post-bac?
Not really. Assuming you're already carrying a pile of student debt, I recommend working out what you are still eligible to borrow, and look hard at any private loans you already have that have rigid limits on deferrals (and definitely don't consider private loans for your postbac - this will cripple you a few years out). For your postbac, fed loans max out around $10,500/yr, and it takes some work to get that to happen. But look at the better programs like Bryn Mawr, Goucher, Scripps to get an idea of how their students finance the program.
Also, be aware that it's perfectly common to have $250,000 student debt on the other side of med school. Assume you just have to do this if you proceed.
(4) How do you make a post-bac application better? Is it like college applications with extracurricular activities, recommendations, etc?
More like a med school app, for structured programs. Start collecting faculty recommendations now, from anyone who will give you a strong positive. You should start clocking clinical volunteering hours right now and don't stop. Find your SAT/GRE/LSAT scores.
You don't have to do a structured program. You can take prereqs at any undergrad school. Look at Harvard Extension, Berkeley Extension & similar. The best school for a postbac is the one where where you can get A's and manage your debt, imho (but I should have done Bennington, d'oh)
Best of luck to you.