How much is wife entitled in repayment of 20% down payment money on house if social security money was used from sons account?

Under Wisconsin  law, all property is presumed 50/50, unless received from a third party as a gift or inheritance. You have $28,000 in equity from your numbers, so your wife would be entitled to one half or $14,000 and you would have to refinance the mortgage to have her name removed. The court can deviate from 50/50 based on factors listed in 767.61, but you have offered no facts in your post as to why this may be applicable  in your case; I didn't understand the question about the source of the down payment being social security money or what the pension buyout has to do with anything.