@Thomas ****
you can't use the income your wife makes for you to get an extension. You either bank the money OR you get the notarized affidavit of income letter from your consulate.
Remember, while it's rare, the immigration officer CAN ask for proof that the amount you put on the notary letter is actually backed up by something (bank deposits, pension letter, etc).
I personally wouldn't put anything on the letter from your consulate that you can't prove.