DTAA -India & USA

Hi ! 

Pls can u solve this below:

My client is a resident staying more than 182 days in india for the F.Y 2010-11. He earns salary in india for part of the year and  salary in USA for remaining months of F.Y in dollars.

Now since he is resident he needs to file the return in india.

Tax deducted at source in USA will be taken as credit in indian income tax return as per Sec 90 of IT Act. 

The tax deducted in USA are in different terms like Federal income tax, Social security(FICA),Federal medicare, California income tax,California state disability....

ISSUE 1: Now whether all the above taxes can be claimed as credit under sec 90.

ISSUE 2: OR , whether these taxes can be claimed as deduction from the salary.

ISSUE 3: Since the salary in USA and tax deducted thereon are in dollars, what is the currency exchange rate applicable to convert the same in rupees in income tax return.

Thanks in anticipation.

Harish Katigar