Office 64bit can be re-installed to 32bit in 4 minutes : #Fritzerklärts:

Use Microsoft Office 32Bit - Office 64Bit is not supported

A support of the 64-bit Office variant is not possible because Microsoft does not allow extensions in the scope of TAPICall. Microsoft itself recommends Office 32-Bit to use add-ins and makes it clear that there is no performance difference, except when using 2GB Excel spreadsheets:
Uninstall the existing Office 64-bit, then install the 32-bit version. You do not have to make any further settings or save your emails. These data are not changed during the uninstallation and automatically integrated into the 32-bit version. The process does not take 5 minutes (vgl. Video).