Art is never finished, only abandoned.
The descision to redo the nose and so on is surely the right one, you need to be happy with what you create, but at the end of the day I truly believe that there has to be a cut-off point before a person goes insane with detail on a project.
I'm the same with the AWIL wolf head I'm currently sculpting, reworked so many areas so many times...it will never BE the screen used piece, but I'm compromising my expectations into a philosophy that it is my TAKE on the screen used piece.
Your sculpt looks great anyway mate, keep up the good work and I look forward to seeing the results - I'm sure they will be ace!
Al