Must be very tough to start something like this while still holding down a full time job.

Hard to say how much time is spent developing vs marketing. Probably something like 90% design, development, user support, and 10% marketing. Where marketing means writing blog posts and engaging on social media (mainly reddit, facebook, twitter).

I tried some paid advertising experiments a couple of years ago but they didn't work well at all. May try another experiment this year now that the product is more polished and has a higher value.