Your model seems pretty sound, Danielle. The only other thing to factor is the opportunity cost of being an attorney a year earlier.
Hard to measure. Especially in local government, there are attorney jobs that don't pay $50,000. Then, some attorney jobs with the fed pay close to six figures to star.
The last thing to point out here is that 4 years is a long time. Supposing you can prove me wrong and somehow graduate with a JD in 4 years part-time, you're talking about 4 years where you won't have a moment to breathe. It will, quite likely, be the worst 4 years of your life, short of being sent to prison.
(And some weeks, you'll probably think prison doesn't sound like such a bad alternative.)
Going to Baylor full-time still lets you live some life for 3 years. Going to st. Mary's, commuting and working really won't ever leave you a spare minute, best-case. That's the best case. I won't keep harping, but I don't see how best-case is possible. You need to at least consider the possibility that you're setting yourself up for failure and that you will flunk out.
You seem to have some grasp of quantitiative tools.
Consider this:
Wake up at 7:00. Shower, dress, rush to work.
Work from 8:00 to 5:00 with an hour break for lunch.
Drive 1.5 hours to class. Park instantly, start class at 6:30. (Most night programs, it'll start more like 5:30, but I'm being generous, here.)
Class until 9:30. Drive home. Arrive home at 11:00.
Fall asleep instantly. Get 8 hours of sleep. Repeat the process for 3 days a week.
I mean, do you see how unrealistic this is? When was the last time you got out of your car, instantly got into bed and got to sleep?
Okay... what's missing here? Oh yeah, studying. Rule of thumb in law school: 1 hour classroom = 3 hours of studying outside of class.
27 hours of studying during the remaining 4 days a week. So, during two work-nights, you study from maybe 5:30 to 10:30.
17 hours of studying to do on the weekends. Relatively short days. You only have to study 8.5 hours each day.
There is zero slippage mixed into any of this. Not one minute to get a sandwich. Not one minute to buy groceries. Not one minute to do laundry. Not one minute to turn on the TV. Not one minute for facebook.
If you take your research and writing class, it'll only count for 1 or 2 credit hours, and you're going to have to spend a LOT of time on it. (I spent more time on research and writing than any other class.) So, add more hours. Some of them will have to be in the library. It'll be mandatory. So will Lexis Training. So will Westlaw Training.
For 4 years.
Are you starting to see where I'm coming from, here?