1. Can the antibiotics I took soon after exposure mask the results at week 10. I read that on the internet or are my results 100% conclusive?

2. What are the odds of syphilis after my 1 unprotected sex encouter?

1. Your 10 week results are absolutely conclusive.  Unfortunately, the internet is full of mis-information, some of which is out of date, some of which is taken out of context and sadly, some of which is just plain wrong.

2.  Your partner was unlikely to have syphilis.  Syphilis is more common in men, particularly men who have sex with other men than in women.  In addition, she is in an age group where syphilis is quite uncommon.  Unless there is a reason to think otherwise, there is a much less than 1% chance that she had syphilis on a purely statistical basis.  if she did have active syphilis, following a single exposure, syphilis is transmitted about 25-33% of the time.  Finally, your test result s PROVE, without a doubt, that you did not acquire syphilis.  

I really would not worry and see no need for further testing related to this encounter.  EWH

So, the  6 , 500 mg of azitromicin I took soon after exposure would have no affect whatsoever on the test results at 10 weeks? Also is the TPPA test a very reliable test?

The TPPA is an acknowledged and very reliable test. 

As Dr. Handsfield and I have both tried to indicate to you, you appear to be worrying about this far far more than is necessary.  I urge you to accept that you did not acquire Syphilis. EWH.

Last question and I apologize for my anxiety filled questions, but I plan on getting back with my ex and we do not use protection, so I guess that's where the concern comes from.

1. In all your years of experience, has anybody in a situation like mine or similar ever became positive later after testing negative??

2. Can I go back to unprotected sex with my ex. 

1.  Never.  It is unheard of.

2.  Yes, without any concern 

EWH