I checked theTaxBook (Sect. 8, Business Deductions). Apparently Surviving Spouse is treated the same as Single or MFS when it comes to the QBI phaseout limits. I had assumed, apparently in error, that it would be treated identically as MFJ. I welcome any further clarification of the regulations.

P.S. I had a typo in the original question. The QBID form is 8995, 8895.