Still a learner here but I will try to comment and answer your 5 questions based on my current knowledge and experience
1. I don't know if there is a magic number or percentage but don't steal every CO ,BTN or SB try to keep it within rational frequencies. If you always do it you will get exploited, sooner or later.Don't open raise only premium holdings.
2.The general rule says when the antes come in play , I play small stakes so not really something that bothers me at the moment in order to improve ASAP.
3.I don't know what you mean by ''complete air'' here. Hands like suited/unsuited connectors 67+ , suited one gappers 79s+ or something like J8+ and some suited Qx,Kx are fine for stealing attempts. Hands like T2 , 93, J3 are auto fold.
You have to think here that most of the times a weak opponent will put you ,most of the times in Ax , Kx type of hands so if you hit big this is where you exploit that kind of players who never fold their top top pairs etc. Always use this mixed strategy in your game. The deeper the blinds the better for you to mix up your open raise range , your steal range, 3bet range and the list goes on.
4.Apparently this is depend on how deep is your stack , with approximately 20bbs you can open raise, with stacks like 10bbs-15bbs is marginal to open shove. With some hands you can't open raise and fold to a 3bet shove. Some hands like mid pairs.They are more +EV to open shove than open raise/call. By shoving you apply more pressure to your opponents and you put them in the tough spot to call for their tournament life.I believe you can understand me here.
5.Nobody open shoves with air from EP , take a look at this very useful link:
https://floattheturn.com/wp/pushfold/
You can use this tactic if you are the chip leader by far and you are playing a satellite and you want to collect all the dead money effortless. Even the open raise tables are math based and show what range to open from what position.Math never lie as far as I know