Your realtor should be able to review the comps and tell you if the ppsf you quoted is above/below average.
You are purchasing at a time when the market has completed a significant leg up. Additionally your ppsf is to generic as ppsf varies based on home size. Average ppsf for a 2000 sf home in 4S will be much different then average ppsf for a 3500 sf home.
Yes there is a downside to Mello Roos but if you want to live in a relatively newer home then you will need to get used to it. Don’t count on MR fees going away or being paid off soon. I would not recommend paying them off early as you never know what curve balls life will throw at you. If for some reason you had to move in 4 years you would feel awfully foolish if you paid them out early.
Your guidance is work with your agent and demand a thorough analysis from them. That is what they do to earn your money. If you don’t trust them, go find someone you do trust.