None of which they have an Art 1 Sec 8 power to be doing in the first place. That is like trying to justify murder because you stole something...
Now you are being silly. These programs are not going away nor are federal pensions. There are suvivorship issues that involve taxpayer money. The federal government needs a definition of marriage to administer its programs, laws, and regulations. Spousal rights exist across an entire spectrum of federal laws and regulations. It is a practical matter that DOMA tried to address. SCOTUS will get involved regardless.