Is social security income federally taxable income for married filing separately if it plus pension and dividends and ira distributions exceed $25K?

Yes, your social security payments can be taxable if your total income, including your Social Security plus any other income, exceeds $25k.

Unless you live in the countries below.

Yes.  In fact even if you have  0 other income.   That's one of the disadvantages of filing Married Separately, you have to report SS.  Is there a reason you are not filing a Joint return?  

Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:

Married Filing Jointly: $32,000

Single or head of household: $25,000

Married Filing Separately: 0