Rpr was non-reactive 6.5 weeks post exposure risk and 1 week after a sore healed. sore was on penis, began as a tiny red dot under skin, then cracked skin, the .5cmx1cm painless flat ulcer. what is the accuracy at 6.5 weeks considering the sore?

RPR always becomes positive within 2 weeks of onset of a syphilitic chancre, so the non-reactive result a week after it healed is conclusive. In addition, your description of the sore doesn't suggest a chancre. You can be sure you do not have syphilis.

RPR positive rate at 7 weeks post-infection is close to 35%. Retesting in 2-4 weeks is advised.