Unless there is a mistake in your dates, you are concerned about HIV from an exposure 2 and a half years ago. Just have an HIV test; if it is negative, you weren't infected. The negative HIV test 3 weeks after the event is slightly reassuring, but too early to be sure. All the details about your symptoms, sexual position, etc make no difference.
To your questions:
1) Alcohol intake doesn't affect the chance you got HIV if exposed and doesn't affect the HIV test results. If you are in the US, the chance your partner had HIV is low.
2) Mouth pain isn't a symptom of HIV. I never heard the term "burning mouth syndrome" and don't know what it is.
3) If your penile burning hasn't been evaluated professionally, you need to do that. However, it is unlikely you have been carrying an STD for 2.5 years. It isn't a symptom of HIV.
Bottom line: Since you're nervous, have an HIV test. I expect the result to be negative.
Regards-- HHH, MD
tested -ve at six week and alter turn +ve.