Trust your gut instinct over spreadsheets. There are too many variables in the real world that you simply can't put into a spreadsheet. Spreadsheets spit out results from your inexact assumptions and give you a false sense of security. In most cases your heart and gut are still your best guide.
Children are supposed to help hold a marriage together. They do this in a number of ways. For instance they demand so much attention that a husband and wife concentrating on their children fail to notice each other's faults.