If my hiv ab/p24 ag screen was negative at 40 days (2 days shy of 6 weeks) past unprotected sex, is it considered accurate?

Yes, for all practical purposes. It almost never takes the full 6 weeks.

No. A negative result at 40 days is about 99% accurate. HIV test window periods https://www.cdc.gov/hiv/basics/hiv-testing/test-types.html Get HPV, Flu and Covid vaccines. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines