Directly to your questions:
1) Both
azithromycinAzithromycin
Azithromycin 3 day dose pack
Azithromycin 5 day dose pack
Azithromycin ophthalmic and penicillin are 100% effective in curing incubating syphilis.
2) If you mean symptoms of syphilis, the question is irrelevant; given the treatment you had, there is no chance you have syphilis. You can read any number of websites about the symptoms of syphilis. Generally the first sign is a painless open sore, most likely on the penis, appearing 3-6 weeks after exposure.
3) Syphilis risks vary geographically and by population group. If your commercial partner is an ethnic minority in a southeastern city, or along the Mexican border, her risk of having syphilis might have been high. Elsewhere in the country and in non-minority populations, extremely rare--and reported syphilis is entirely absent in many states in the US.
Bottom line: You have no STD worries from your recent adventures. Best wishes--
HHH, MD