PLEASE Various grammar questions

Help understand which is correct please.

in the dictionary impact is followed by on not in?
1 How much impact does that have in making your decision?

which is correct?
2 He's known as a defender/for his defense./to be a defender.

What to do with 'in'?
3 I did the right thing (in) doing that.

amount of points is correct?
4 When you are down this amount of points, you need to play better.

fast forward through is correct?
5 The show I fast forward through most is this one. It's so boring.

Whats wrong with --->
6 She can buy a plane others buy a t shirt. She is that rich

thanks in advance