To answer question 6 in the original email - would the lender pursue the debt in the USA -(posted 9070 days ago)The answer is yes then can pursue you, but its down to the individual lender and the amount owing whether or not they would actually bother to do this.
Also, if it does go to court and the court believes you Son didn't know he was a partner in the mortgage, then the mortgage company could well bring a criminal prosecution against you for obtaining funds by deception and/or forgery - again if you are in the USA then they may not bother because of the expense involved in actually finding you.