I don't have comments regarding the entire post, but I definitely have one regarding the size of the project: stick to something smaller that you can push out (at least in limited form) in your four-to-six-month timetable. If you choose something that will take you almost two years to launch but you can't commit full-time to it, then there will (most-likely) always be others with a similar idea who can work more hours or get their product out faster. Even if you didn't see competitors for a whole year, you'll still be stuck in part-time mode. On a two-year, part-time schedule, you won't be able to react at all to movement or changes in the market you decide to go into.

That's why I'd suggest sticking with something a bit smaller and a bit more manageable that can launch early and grow slowly over time, which is much better-suited to your schedule and existing commitments.