I was married for the year 2007, but was forced to file as single, as I got separated from my spouse in 2007. I got divorced in 2008 and subsequently got married again to a different person in 2008.

Can I use my current spouse's SSN/ITIN to file amendment for 2007 to file jointly (or even separately) .

No, you cannot, because you were NOT married to that person in 2007.

If you did file such an amendment, it would be considered TAX FRAUD!

No! You were not married to your current spouse in 2007, so you can not amend your return for 2007 to pretend that you were.