Some people say that you gain faster if you have NOT been circumcised but it is all speculation. Unless your skin is super tight when erect, I don't see circumcision hindering your gains.
Your wrap could be too tight constricting blood flow. How long have you been hanging because 25 lbs seems a bit excessive? My head may be slightly numb when my set 20 to 25 minute set is finished but never longer then a few seconds. You definitely are doing something wrong.
I say hanging is best for length gains. I don't think extenders are worth the cash and you can make a good homemade hanger for $20-30 or get a bib hanger for like $100.