1) 6 2) no 3) M-[2-9] 4) tab-line + config 5) not yet
I have things set up so the most recent buffer is always the left-most tab, and the tabs are sorted by most recent usage, up to 6 shown. Makes it quick to switch among several recent buffers. I usually track this in my head for 2-4 buffers, the tabs are a crutch for more than this or when I am not sure.