I think in cases like these, you're more likely to get a response by adding another post as a reply to the person with just a single unanswered question (start with the one you care about most), so the person will see they have a new response in their inbox and realize they never answered an earlier question. If you post each of those 3 questions as a response to the person, in context, I'd be very surprised if you didn't get a response to at least 2 of the 3, as long as you include little to nothing else in each post so it's obvious what you're asking for and they can't respond to something else in the post. I've noticed that longish posts with multiple questions often get just one question answered and all the others ignored, intentionally or unintentionally. And posts that are longish with questions interspersed with non-questions tend to get responded too as if the non-questions were the substantive part, with the questions often ignored. (The other extremely common reason for not getting a response is identifying a flaw or asking a question that shows problems with the person's position, in which case most people seem to just ignore the post rather than admit they were wrong or can't answer a critique. I don't think that's the case here at all though.)

Not answering a question is Internet's way of walking away from a conversation. You don't usually say "excuse me, I'm late to a meeting", as interaction is asynchronous. In the current Internet culture, saying "I don't want to bother answering" sounds rude, and so the best solution signaling-wise is to just not answer.