Perhaps a quick chat with patio11 would help here? I can't imagine a more appropriate HNer for the kinds of questions you have. He has been thinking about the education market for quite a while. He has long advocated finding freelancers who you can pay to build up content. What about hiring some freelance subject experts to build questions for you? That removes at least one burden to expansion and lets you trade money for time. Along those same lines, you might focus your energy on automating as much of your maintenance as possible so that you can focus on developing novel stuff. Maybe even hire a freelance web developer to do some of the more boilerplate stuff so you can focus on the truly unique stuff.