Reg: Visa screen certificate

Hi, here is my case detail,

Actually the NY board has evaluated my credentials and accepted the same allowed me to contact FSBPT to take up the NPTE from May 2011 onwards. Currently working in Oman.
My husband, a Pharmacist is now in US on H1B visa .I am planning to go on H4 visa and give NPTE in next year later upon passing change to H1b to start working.Right now I am in the process of getting done my Visa Screen Certificate.Now my doubts are,
1)should I get a visa screen certificate for Greencard (Permanent)job or for H1B job?
2)can I go to US on H4 and later convert to H1b?Is it possible? or will it affect my greencard job process later?
3) Are there any new rules have come up in regard with ATT for NPTE esp for foreign PTs like Indians?
I absolutely have no idea on how to go about in these entiire process.I want some sincere advise.Please guide me. Thank you in advance.