optiix

Since it is market value, the bond with or without option is already priced by the market. You need to know that regardless of using Z spread or OAS, the intended outcome is to make the discounted value = market value.

spreads

Q1 could be over or undervalue. Triple a =\= riskiness since company can’t print money. Also there is liquidity risk. You not sure if the credit risk plus liquidity is risk is worth more or less than 70 bp.
Q2. Over value. Ur earning less than the spot rate. It means that credit risk and liquidity risk is negative, which is impossible. It’s better if you just purchase a treasury bond