Anyone please help me with correcting hard sentences

Could you please help me make these sentences grammatical?

1 The heater in the room is there to make up for the breeze that comes in through the gaps in the window frame.
2 By the time I (had) picked up, you had hung up.
3 The change in temperature is hurting my back the way it is/like this.
4 Do it as you go/progressively.
5 Try to get your son's principal to make/get your son (to) graduate by any means necessary, even if it means paying her off.
6 The computer froze at the perfect time. The process had just gotten to 100%.
7 If you don't come for dinner, we'll have 2 people less to feed.

Thank you