If you are not taking a Deed of Trust on the house, I'm not sure you will be able to rely on the dwelling being available. Afterall, the owner can easily get a home equity loan or line or junior liens and zap all of the equity out of the property.
A bank I used to work for would have the Deed of Trust secure the guaranty, and the spouse's signature on the Deed was sufficient according to their legal counsel.
You may want to ask your legal counsel about the "limited" guaranty, or of filing a Deed of Trust to secure the guaranty.
Reg B is fine about requiring the signature of the spouse on a document to make collateral available.
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CRCM,CAMS
Regulations are a poor substitute for ethics.
Just sayin'