Welcome to HCM.
Itching of penis and adjacent areas are not symptoms of Syphilis
. It may be due to various other causes like fungal infection
Some of the tests done for Syphilis (Specific tests with Treponemal Antigen) will be persistently positive for ever even after adequate treatment. That is called as Serological scar or Serofast. That doesn't warrant further treatment if adequate recommended treatment is completed once. Most of the card test are available only with Treponemal antigen. So it will show a persistent positive result only. Not to worry for that.
Rapid Plasma Reaction test is nonspecific test for Syphilis and has a prognostic value following treatment. The titre will come down following adequate treatment and will become nonreactive after 6-12 months of specific treatment.
Sometimes associated HIV
infection also may be a reason for persistent titre.
Get well soon.