Welcome to the Forum and thanks for your question.  From reading your question, my sense is that the only thing that will really resolve your concerns is a test and I would urge you to do so when possible.  I hope that the information below will help to reduce your concern however.

You suggest that perhaps your partner had become infected in the interval since his last test.  I would remind you however that since I suspect that he was a CSW for some time, having avoided infection to date makes it likely he will continue to do so. Further and parenthetically, for future partners, you might also ask them if they are taking PrEP since it is widely available and a male CSW would be a reasonable person to take it, given the occupational risk. 

The exposure you describe was low risk, even if he had HIV.  The risk of acquiring HIV from performing oral sex on an infected partner is, on average, less than in in 10,000.  Thus, even if he was infected, your statistical risk low and chances are, on average, 99.99% that you would not be infected. 

Finally, while the timing of your flu-like illness does coincide with the time that the ARS might occur, it does not have all of the features of the ARS and, even if it did, it would be far more likely that you acquired a typical, influenza-type, non-STI viral illness than HIV.  The classical ARS include HIGH fevers (yours are not) and a severe sore throat as well as muscle an joint aches..

Bottom line, your risk for infection is quite small.  Nonetheless, I think testing is reasonable.  If your current illness is HIV a HIV PCR test will be positive at anytime more than 11-12 days after exposure and a 4th generation, combination HIV antigen/antibody test will be more than 99% reliable at 4 weeks.

I hope this information is helpful.  EWH

thanks for your follow-up questions- they are good ones.

1. When the ARS occurs, symptoms are typically rather severe and all occur at about the same time.

2.  A solitary lymph node is highly non-specific and would be quite unusual in the ARS.

3.  I urge you to stay away from Google for this purpose.  As you have experienced, most any sign or symptom looked at on Google will have HIV listed as a potential cause.  Much of what is there is either out of date, taken out of context or just plain wrong.  Night sweats are non-specific.  Common causes include gastric reflux and just about anything that can cause a viral sore throat.

Particularly for early diagnosis of HIV symptoms a combined HIV antigen/antibody test is better and provides more accurate results than antibody only tests.  They are widely available at most places where HIV testing is performed.  EWH