Thanks for explaining your situation.
First, it does not sound like you will be sued for defamation, based on what you described in your post and based on the fact that defamation actions cost thousands and thousands and thousands of dollars to pursue. They are rarely worth the time, effort and money unless the reputational injury suffered is so severe and so easily demonstrated that an action makes sense.
Nothing really prevents someone from attempting to sue, however, so if the person defamed is the litigious sort, you are wise to be concerned.
If you are seriously worried that you will be sued for defamation, and you believe you have enough assets to warrant the expense of an umbrella policy, it would be wise to have this additional liability coverage. Consult with your insurance agent for details.
As for the IRA and house, any asset can be targeted in a judgment. Some assets targeted may be exempt, however, and others may be denied by the court. IRAs, for the most part, cannot be used to satisfy a judgment, although state laws vary on this, and you would need to consult with an attorney in Illinois. Houses can have liens placed on them, to satisfy the judgment when the house is sold, but a sale cannot be forced.
I would have a brief consultation with an attorney, and review your situation with him. He can give you a better idea of what you need to do to protect yourself, or even if he believes extra protection is needed.
Good luck.
