A mod might be more qualified to answer this than I am, but looking over your questions, a few things pop out:
Be specific. This question is incredibly broad, covering everything from Hannibal to Napoleon in Europe alone. Likewise, questions about "the Middle Ages" cover an impossibly wide sweep of time, space, and cultures.
Understand how academic history works. You have some really cool questions in your history, things that I would LOVE to see historians both here and in the field tackle more. Still, most historian's brains don't default to describing how a city street might look or providing prose descriptions to the change of a landscape over centuries. I would love it if we did, and I think it would be good for the field if we were more comfortable writing like that. Still, until William Cronon opens an account on here, we're hard up for environmental historians that can do that kind of writing.
Luck. You have a few questions I'm surprised did not get answered. We get busy around here, especially during paper, midterm, and finals seasons. Sometimes, a good question comes up when the relevant big gun just doesn't have the time to answer it. I hate when this happens.
Try pinging relevant flaired users. I haven't seen this done much, but know that I felt an increased sense of immediacy and urgency the times I've been specifically mentioned or PM'd.
I hope this helps, and that your future posts get more noticed than they have been. Good luck!
If you have a question that you really love and it didn't get any attention, post it again in the Sunday Digest. I, at least, am trying to make a habit of picking out an unanswered question from the past month or so and answering it in Saturday Reading or the Sunday Digest on a weekly or semi-weekly basis. /u/LukeInTheSkyWith has been so awesome at highlighting a few unanswered questions each week, and hopefully more people will start to get in on answering them. :D (And posting their answers in SRR/SD/Friday Free-for-All, so I get to read them, too!)
The other thing is that threads are much more likely to get answers if they are popular, so when you post is often an important consideration. Stuff that goes up in the morning US time--the start of the workday on the east coast--usually gets the highest visibility for the most popular ones, but also has the most competition. Early afternoon US east time is also strong. Stuff posted overnight in the US generally gets ignored (although there is the occasional exception...reddit's algorithm is odd).
Aside from what has been said here, we have three Roundtables that address this topic in different ways.
Rules Roundtable #16: There Is No Such Thing as a Stupid Question
Rules Roundtable #17: Periodization and Regionalization
Rules Roundtable #18: How to Ask Better Questions
The last one in particular I'd recommend you check out. None of these guarantee an answer, but they do make your questions stick out more for the right people.