For the Qs. no 1.
No. I don't think it's the saying "just knowing whom to trust." that is the factor hardening the jobs. Rather "JUST KNOWING WHOM TO TRUST" is the job that's getting hard.
The factor that's working behind hardening the job is the outer good appearances of those bad guys.
For the Qs. no. 2.
The underlined part is grammatically correct.
What I think is: -
The line is saying that they [THOSE PEOPLE] will last a long long time because of the experience they had from those shocks, deaths, violence etc.
It's not the memories of those experiences that will last for a long long time.
NOTE: - I could be wrong in both my answers because I'm still learning..
I too would like to know what experts have to say