On your #1, the biggest change is "private label MBS" (which did not get the GSEs' guarantee) largely vanished from the market (the high since the crisis was a twentieth of 2007's number). The supermajority of investors in pools of mortgages are buying GSE-issued securities, which are insulated from default risk, including the case where the lender seizes the collateral and can't liquidate it for the entire outstanding principal net of costs.