I think all of the advice you have been given is very helpful and sounds quite positive.
I used to work in sexual health as a nurse and I know that if someone tested positive for Hep B antibodies we didn't straight away asume they had active hepatitis. It often just meant they had either been exposed to the virus in the past, or had been previously vaccinated. Further more conclusive tests were then done to see if the disease was active.
If my dog was healthy and tested positive, with high antibody levels, I would be questioning whether they had been recently vaccinated and whether the rise in antibodies was just the normal reaction to the jabs.