1. I'm sort of surprised to hear part-time econ doctorate programs exist. If you're near one, though, I'm sure they're offered as a money maker for the college (and you will be paying dearly, my friend), and not as the research-centered free-slave-labor programs at major universities. So, I'm sure you and your friend Mr. Franklin will be quite welcome.
2. You'll be fine on math.
3. There are so many good professors (in my opinion, often more than the big names) at these smaller colleges for people who just want to learn. The idea that MIT or Harvard must have great lecturers (although they do have a few) because they're top-ten doesn't really make sense - they're top ten for research, and research professors don't teach much and usually don't make exceptional teachers. I'm sure you'll find some good souls at Suffolk, and I'm sure you can audit some classes first.
And actually, just looked up Suffolk on UNWR. Ranked for the region, so not bad at all.
4. Can't really help you there, as I didn't know part time PhD's existed. However, the difference between a more academically-centered MA and a PhD is often just the dissertation, and I'm not sure if you're really interested in writing one of those. Maybe you are though.
5. I can only answer from my perspective, which is of course it's worth it.