Welcome to the Forum. There is virtually no risk that you have syphilis from the encounter that you describe. Syphilis is a relatively rare infection, condoms offer very good protection if your partner was infected, and acquisition of syphilis from receipt of unprotected sex is extraordinarily rare. Further the 7 days of doxycycline that you took would have prevented syphilis if you had been exposed.  The scalp bumps and hives that you describe are not particularly suggestive of syphilis and given the other facts surrounding the encounter that you describe, I see absolutely no reason for you to be worried about syphilis.   No need for additional testing as well.

I hope these comments are helpful.  EWH

Syphilis itself is rather rare in the United States, fewer than 15,000 new cases in a country of 350,000,000.  Further, about 2/3 of syphilis now occurs among men who have sex with men..  Finally, as I informed you, the antibiotics you took would have reliably prevented syphilis in the extraordinarily low chance that you were exposed to syphilis. You need to stop worrying and move on.

This is my third reply to your questions therefore, as per Forum Guidelines, this thread will be closed later this evening.  EWH