First, are you sure the wife can not be considered head of household? The qualification for head of household to be exempt from garnishment is not the same as the IRS Head of Household designation. You should probably consider scheduling an appointment with an attorney experienced in asset protection and debt relief before making that determination.

Second, there are no exemptions from garnishment for hardship in Florida.

Third, if the judgment is in the name of the wife ONLY (and assuming you live in Florida) then any assets held jointly with the husband or another are likely going to be exempt from garnishment/levy (however there are some exceptions so again an appointment with a debt relief attorney could be helpful).

On a side note, you mentioned the trial payments on your loan mod take all of your combined income. That does not sound sustainable for the long term and it may be something you need to consider. If you have not consulted an attorney experienced in foreclosure litigation/prevention you may want to do so before entering into any modification programs. There are significant problems with many of the trial modifications that are being entered into and you really should be aware of your rights and options. You may have options that you are not aware of (don't take the bank's word for anything. See the recent news of how Bank of America employees were directed to lie to homeowners and trick them into default so the bank could foreclose)

Finally, if you have a large amount of unsecured debt (i.e. credit card) you may want to consider bankruptcy as an option. While it should be an option of last resort, it MAY be something that can assist you in all areas of concern. Again, you should talk to an attorney with experience in these areas of law.

Good luck and I hope this answer helps.