The Defense of Marriage Law is out of their powers and them trying to get gay marriage is also out of it. It is not one of the enumerated powers. His whole thing is that it is not a federal power granted by the Constitution.
As for abortion it also is not a federal issue it is not covered by the Constitution it was made up by the USSC.
http://en.wikipedia.org/wiki/Defense_of_Marriage_Act: "Under the law, no U.S. state or political subdivision is required to recognize a same-sex marriage from another state." (emphasis added)
That clause is exactly a forswearing of power not an exercise of power.
"Section 3 of DOMA codifies the non-recognition of same-sex marriages for all federal purposes, including insurance benefits for government employees, Social Security survivors' benefits, immigration, and the filing of joint tax returns."
You can argue that the federal government shouldn't provide any employee insurance or Social Security survivors' benefits, or regulate immigration, or collect income taxes - but if you grant that any of those are as a whole within their powers, you can't then argue that setting specific policies in those areas is outside their powers.
and them trying to get gay marriage is also out of it.
How exactly (apart from DOMA) are they "trying to get gay marriage"?
As for abortion it also is not a federal issue it is not covered by the Constitution it was made up by the USSC.
And since the federal court made it up and is unwilling to unmake it, only action by the other federal branches can rectify that - those actions are in defense of the Constitution not in violation of it.