Can I add the total of 2 SA1099 forms? I received 3, 1 for my husband, mine, and then another issued with a "D" at the end of the claim

[JohnW152]

No, don't add any of the forms together.  You should never change information on information returns that you receive.  They're issued to you, but also shared with the IRS.

Does one of these appear to be a corrected form?  If you can't figure out what the unusual form represents, you should contact institution that provided the forms.