As someone whose dream is to do something similar, is it too rude to ask how much money you started off with and what other income you have, if any?
I'd managed to save about £40,000 GBP by the end of 2012. Then in 2014 I took some months off from Readlang and earned roughly £30,000 GBP doing some contract work. No other sources of income. I've never been close to running out of money, if I did I would certainly ease back on Readlang and look for more freelance work.
BTW: The freelance work I did wasn't using technology I enjoy or want to focus on in future, and was offered to me without having to look for it. I did it because of the money and because I liked the people. I've never actually had to actively look for freelance gigs myself. So I'm still not sure how easy it is to find good clients with interesting work.
I currently work for a small start-up also working in the education sector (albeit more directly). The general story isn't too dissimilar to yours, though, in that it's been a bit of a slog for not a huge amount of profit, although things are slowly looking more and more promising.
I wish you continued success with Readlang.