I'll give this a shot as a GBS survivor and someone who recently settled with the Nat'l Vaccine Injury Compensation Program (NVICP)

1-- GBS can occur with any "thing" that makes a person's immune system respond. It's sort of unknown why it happens, but it CAN be caused by viral infections. And because vaccines induce the immune system to react as if it has been attacked by the virus it is protecting against, the vaccine can trigger GBS.
2-- I'm not sure that you can assume that vaccines aren't responsible for the rise. I'm not an expert, but the increase in frequency of these "staged attacks" on our immune systems (ie vaccinations) may just cause the immune systems in people who are susceptible to auto-immune disorders to overreact, where maybe they never would have if their bodies weren't inoculated so frequently.
At any rate, the NVICP only requires that the victim show probable cause that a vaccine caused their GBS. Their range of probable cause includes symptom onset within 6-10 weeks of vaccination.
3-- I've read this too... don't know if it is still common knowledge.