Did you or your attorney file QDRO? Going on your question, how would the party holding the 401K KNOW that they needed your signature?

Can he legally never notify me that he withdrew that money and pay bills on his own accord?

A proper QDRO would have allowed you to remove half of the money from his 401k when the order was signed. It could have been rolled over into your own retirement plan, or you could have taken the withdrawal, and paid taxes/penalties like any other early withdrawal. In either case you'd have control over your half of the 401k you were granted in your divorce.

Besides, leaving your half comingled would be a terrible thing to try to figure out what your portion would be if you stated taking money out years down the road.

With additional contributions by him and the nature of the 401k itself how do you know which part of the investment is yours. It's not like you got 500 shares of one stock. Most 401k plan porflios are diversified across a range of investment products which are routinely traded with losses and gains happening.

Anywho, what a mess.

I never reccommend the action that was taken in the above case;merely a vague court order to "split it with her" again with no finite terms, etc.
I don't even like QDROs. I like it when the holder of the plan has to just pay that person cash, i.e.half of the value of the plan that date; paid by a loan or min monthly payments.

I assume from her second question she did not get QDRO, so, now she will hhave to have her attorney motion for a show cause as to why he violated the court order, and get a new judgmnet against him, or seize some other property to sell to satisfy . It obvious now ( and it should be to the court) this man cannot be trusted even when under a court order, so harsh action needs to be taken.

Make sure and ask for atty fees since he brought this situation about by defying the court. Her former atty should handle this for her without a retainer ( and hope the ct awards atty fees), since s/he dropped the ball for not efforting "due diligence" and asking the court to approve a QDRO.