Most important and in response to your main questions, your conclusions are exactly right:  the combination of those two tests at 4 weeks is conclusive proof you don't have HIV. In fact, the RNA test alone is conclusive any time 11 days or more after exposure. 27 vs 28 days makes no difference for either test.

It's also good to hear you also tested negative for other STDs, which presumably included at least urine testing for gonorrhea and chlamydia, which staistically were the greatest STD risks from these exposures; and a blood test for syphilis. That raises the only slight issue for consideration:  the syphilis blood tests are not conclusvie until 6 weeks after exposure. That said, the risk for syphilis from such partners and exposures is near zero, and absence of symptoms (a non-healing sore at an exposed site, i.e. penis or mouth) is also strong evidence you weren't infected. But if you feel you need the reassurance of a conclusive test, have another at 6 weeks.