You wouldn't add in INCOME from a guarantor, but if the credit decision was based on REVENUES from a related entity you would use the code appropriate to that entity. It would never automatically be a 3.
To clairfy, there is no "revenue" code for HMDA loans. You report "INCOME" not revenues when you report for HMDA purposes. For CRA you report only REVENUE, never INCOME
I'd refer your FDIC examiner to GIR, many comments, the actual CRA...etc., but I think they are misunderstanding a question here since revenue and income seem to be under some confusion...