Activities link

1/ you need to understand the logic between the activities, in a multi story building, no matter how far ahead your M & E is they will never overtake your structure (very basic example used there).

2/ 2% critical activities... without knowing the details of the schedule I wouldnt say this is excessive. Was the comment that there were too few or too many activities?

There is a post here somewhere about % of critical activities with some good comments.

3/ the way i usually impose an end date is to apply a late constraint to contractural completion dates (PC or completion of separable portions) this way you can use negative float to analyise the real float of your activity chains and see where acceleration is required to meet programme.