The bars are connected for a reason. Leave them alone. To answer your questions:
1. If you seperate the bars, then each and every circuit breaker in the panel might not trip properly on fault. Self-explanatory as to the danger.
2. No. Only one ground is permitted for the whole house electrical system by code.
Strongly suggested: talk to an electrician or your local BD inspector before you touch anything, regardless of what you read here.