It should only buy the missing quantities, if a teleport was used, it will attempt to buy a new one to replace anything that was used; you can pause the script instead of stopping it (the pause button next to the stop button), otherwise it may not continue quests properly
I'm afraid I'm not currently doing trials
It was from 50 min to 3 hours from the tests I've done
I'm afraid I'm not currently doing trials
The script will show all items it will look for right after it checks bank (this is always the first thing it does when starting the script) in the logger (top right corner under Settings -> Toggle logger); a list of required items will be printed, and a list of missing items after that, including quantities
That's a problem with the newest mirror mode version, a new mirror client should be available soon, it's already in testing