"And if I'm wrong and he did have them, then its probable that someone else has them by now. That would not be a good thing. And if this is true, one could not conclude the war achieved its objectives. In fact, the potential threat to American lives would be greater than ever."

At this point in time I think the risk is lower. I also expect this risk to lower further. Look at this way their are lots countries with WMD, if you have the intention, money and connections, you could get your hands on WMD. You could get miltary team together and attack an storage area somewhere- say in Syria. The problem is you would leave a trail which could be followed- and carrying a couple of tons of WMD makes you a easier target. If you looked at the problem: You don't have WMD, and you want to use them in X country, and you have some people who know how to make WMD, and the country where you want to use the WMD, has the techonlogy you need and you can buy it. Then making the WMD in X country could be an easier option, than stealing it, and transporting it to X country.
But, what is the reason underlying this moviation to use MWD? Does the risk associated with getting WMD and then deloying them, worth it- as compared to some other route- such as attacking computer networks, or lots of other options. Saddam had a means, and moviation to weaken US power. The US was actively working against everything Saddam wanted to do. Saddam wanted to use terror and miltary power to destablize the region- the US is the major and well recognized player in the Middle East trying to stablize and bring about better govts in the region. The US wants democracy in the region, Saddam wanted a dictatorship over the entire Middle East and had a dictatorship over Iraq he wanted to protect.