I'm not sure how many people will register.
I do know last year 177,500 people got tickets.
Not sure how many people cant/dont get tickets.
The 1st wave of tickets usually sell out the same day and the 2nd wave in a matter of hours. They have been known to have small unannounced sales between oct and april. You will need to keep checking see tickets, this forum, or follow glastwatch on twitter for more info on this.
I think you can buy as many tickets as you want as long as you have every persons reg numbers and personal details.
I have removed your other post so we didnt get duplicat posts