Great article, and raises some really interesting questions.
It’s obviously a complex issue, and a lot has to do with young girls’ opportunities and experiences in STEM — fewer women programmers = fewer women tech start-up founders.
But looking beyond that, and focussing on women who are already working in tech but not starting a business (ie your #2 point), maybe something to consider is: are we assuming that the motivations and barriers are the same for women and men?
Perhaps we ned research into what drives technical people to become entrepreneurs: what motivates them, and what barriers did they perceive (and/or overcome) before taking the leap?
It could be that the current approach happens to speak more to technical men’s motivations and barriers, and misses something that would fit better for technical women.
It sounds like you’ve already been doing this informally, by speaking to women who could start a business but haven’t. More comprehensive research that you know is statistically significant could be really interesting and get you a bit further along in solving this tricky problem!