Dealing with syphilis

[BritishCumdump]

Hey, so it's finally caught up with me and I've been diagnosed with stage 2 syphilis. Far too many slutty meets and cumdump sessions so I guess I deserve this. It must have dodged the net of my every 2 month checkup and unlike most of the time when I get an std this time it's really symptomatic (red spots, swollen joints, the lot). 

I've had my injections now (I think it was just penicillin) and the doc says it'll be two weeks minimum before I can fuck again which is fine. I just wanted to ask about syph from the community here as the official information online seems vague. 

How infectious is syph usually? Like I've informed the last 15 guys I've slept with and while some have gone and immediately got treated just in case, others have just shrugged and said they feel fine and will see what happens at their next test. Should I be pushing them to go get treated? I remember I got fucked by a big rough dom a few years ago who told me when he was already inside me that he had syph and I managed to dodge it then but is that a rare exception? I might he a cumdump pig but I hope I haven't spread this too far. 

Also does anyone have advice for dealing with these symptoms? I'm trying to rest and not scratch but is it just a case of waiting it out and not spreading it any further? 

Will Doxyprep help me avoid this in the future?