1) Low GPA 2) Employement gap; 3) Can't get recommendation letter from current manager; 4) Low AWA score 5) Who you like better: Jennifer Lopez or Britney Spears?
1) It depends on how low your GPA was. I believe adcom knows who is top university in China, so you don't have to mention this, unless you GPA is below 3.0.
2) Two months gap is not a big deal. Don't worry about that.
3) Yes, if that senior people is also from your current company.
4) Even 5.0 is high enough, not to mention you also had an 5.5 before that.
Looks like you don't need that optional essay at all. Take a rest!