There are no tests marketed or sold to give a conclusive negative test result earlier than 3 months post exposure.
guidelines in the US are 12 week, but your DUO test at 9,10 weeks its EXTREMELY reasuring.
As you said, all tests today would detect antibodies in nearly 100% of people at week 8, and same goes for DUO test at week 4.
regards,
No you are not having ARS symptoms and no 8 weeks is not conclusive.