I'm stuck at the suites level.

It says I need explosives at 35 but I only got 30.

If I have enough do I still have to kill her?

I killed her but couldn't get out on time, what is the fastest exit?

The fastest, and I believe at this point only exit is the elevator to the lobby, where you entered. From Christine's suite go left, through the kitchen on your right, make your way to one more room and go straight to the exit. I think. There's plenty of time if you go through the kitchen.