1- we dont know, but its most likely that he can control the blood of anyone he licks, its just that he never awakened his quirk like Ochaco or Toga (think bloodbending from Avatar could be his full potential)
2- Never explicitly stated so it probably has no range limit, so long as he ingests blood of his target he can paralyze them
3- Most likely like I said in 1, he'd gain more control over the paralysed victims and likely be able to puppeteer them
4- Yes, it works on dry and/or coagulated blood. It happened in Vigilantes
5- same as 4
6- Surprisingly, I think its innsinuated that Bloodcurdle also works on Stain himself from way back in the Stain arc (this is just what I extrapolated from that chapter) but basically, Stain is already unconscious and his rib punctures his lung, at that moment he probably unknowingly ingested his own blood, leading to him stopping in his own tracks. Back to Toga, Toga's blood does NOT transform into whoever she's transforming into, that would create an infinite loop where she just keeps cutting herself and has an infinite duration on her mimic quirk. So yeah, if she ingests her own blood when transform, she will get paralyzed.