#2
Usually they mean slides, but in this case they're probably strums, but listen to the song for the correct strumming pattern, etc...
#3
so does it some times amtter...cuz at one time theres 2 slashes and at others there 4
#4
In my opinion not really, it doesn't matter, as long as you know the chords, just match it up with the way the song is played, or make it your own.
#6
Don't worry too much about the I's, it probably means to go to the next chord. Reading tabs is a voodoo science sometimes, the main thing is that you have the chords to play with.