"16  Check if you are a widower who has not remarried and this home sale was within 2 years of your spouses death and the spouse qualified for the exclusion immediately before their death. ( I checked this box)"

Why did you check the box? You are filing a joint tax return for two people that both died in the same year. The widower is not filing a return.

Did you take into account step up in basis on death of the husband? Possibly the sale of home does not technically even need to be reported. Was there a 1099-S?

Yes she is a widow. She is not filing as a widow. She and her husband are filing, but with her death the signature on the return will not be either of their signatures. Who's gonna sign this return?