Just for additional clarification;
As I said, 401(k) plans are VERY heavily regulated by law. Each one has a plan document and that plan document is CARVED IN STONE. The requirements and the processes in that plan document, CANNOT, BY LAW, be varied one iota. If the requirement is that there has to be a POA on file WITH the administrator (as opposed to the sponsoring employer) before funds can be released (and for the reasons described by Zigner in the post above mine there damn will should be such a requirement if there isn't one) then they would be in violation of the law if they gave your husband access to the funds without a POA on file WITH THEM. There is no provision to make exceptions for people with disabilities; these limits are for their, and everyone else's, protection. What if you weren't who you claimed to be and were manipulating him to get access to his money for your own purposes? The requirement for the POA protects your husband, protects you, and protects them; a win-win.
Now, you have a potentially bigger issue that may make the entire question of the POA moot. I realize there hasn't been much time and you maybe didn't even see my first post before this one, but it's very important; what are you intending to use this withdrawal for? There's a HUGE issue related to that, that could make an enormous difference to the whole situation.