I'm not a lawyer but I would say that yes that is legal. There is no law that states you have to put money into a 401k, it's just a benefit of working for some companies whether or not you take advantage of that benefit is up to the worker. So since he probably saw this coming he decided to stop putting money into the account. Wouldn't you do the same. So you get half of the value on 8/10 does it say anywhere in there that he has to keep contributing? I imagine it just says you get half the value on that date. If so then that's what it is half the value on that date I sincerely doubt the court would make him continue contributing to the 401k or to give you the difference. Good Luck.

But cCan I send our divorce decree with a Principle Co. Form I downloaded from his 401K site for the plan administrator, to get my half as a lump sum...
would this be considered the QUADRO?

You or your lawyer should immediately file the relevant papers with the plan administrator so your ex can't withdraw all the funds and put them beyond your reach.

As to the contributions you feel he should have made between 3/10 and 8/10, I guess the first thing to do is calculate what you think those contributions are worth, figure out what your share would be, and then compare that with the cost, in terms of lawyers and court costs (if any) to get your ex to make those contributions retroactively.