Am widowed filed 1040SR, took standard deductionIRS now wants Schedule A. Why would IRS ask for info to support $22650 on line 12 of 1040SR?

Sorry for your loss.  When did your spouse pass?  You can file a Joint return the year your spouse died. For the next two years following a husband's or wife's death, the surviving spouse can file as a qualifying widow or widower if they have a qualifying child. That basically lets you continue to use the same tax brackets that apply to married-filing-jointly returns. After the year of death if you don't have a child you file as Single. And then next year start over with a new return and new account. 

$22,650 is the Standard Deduction for Head of Household.  Are you filing Single with a dependent?  Maybe they are disallowing the HoH status or your dependent.  You need to call them and ask why.