You completely miss the point of DOMA. Congress was not trying to prevent any state from allowing homosexual “marriages”. It was trying to defend the prerogative of other states to not have to recognize such “marriages” under the guise of the Full Faith and Credit clause (U.S. Const., Article IV, Section 1). DOMA protects states rights, it does not infringe them.
No. I believe you don't fully understand DOMA. There are several sections of DOMA. Thus far, only Section 3 has been found to be unconstitutional. Section 2, which is the section that deals with the part you've described, has been left alone.