1. You cannot go for stamping with that petition if its not supported by the petitioner. Moreover, its almost the end of your petition validity and I believe there is a high chance of denying the VISA.
2. Though highly impossible, if you are lucky and got stamping, you dont need to come back to India for renewal of VISA. You can renew the petition in US only.
An option for you is to go to US on H4 VISA and try to get a job there - you could use this approved H1B petition to file cap-exempt petition and need not wait till April 2013.