If it was me, my financial situation may be different, but, I'd drag myself up by the scruff of my neck and set aside some time to fix it......$10k a year!
I personally find it difficult to work on multiple large software projects at the same time. There's just so much I can keep in my head at once. If it were a few thousand lines of code, maybe, but Magic Maps weighs in around 35 kLoC, and the other one is pushing 100 kLoC. It takes a fair amount of mental bandwidth to dig into deep bugs, and I'd like to save that bandwidth for my other app.
I had a similar situation, and went the route of open source. The product died, as no one but me really wanted to maintain it. It was effectively the same as turning my back on the project while maintaining sales, except without the $$.
I'd recommend you ignore it and focus on your new app for long periods of time. Don't fix any bugs for months on end, then take a little time to knock out the big ones. Ignore the edge cases and focus on the big picture, that this app isn't your big thing, the next app is.
In some sense I've been here before. My very first app was an iPhone app, actually one of the first police scanner apps, with a glowing map of Chicago that got me into the whole software-mapping thing. I had to put that one out to pasture a few years ago, even though I thought there could have been a viable little business in the right hands.