Buy muni bonds from Fidelity

Last week, I bought 10 muni bonds from fidelity. It’s a new issued AA+ OB bond (investment grade). I get a lesson from this trade.
1. You never know what the price you will get is. Later I found my deal is not very good in that day (total 5 trades that day, my price is 2nd high or 1.5% higher than lowest price).

2. The gap of buy and sell is very big. That is, I bought at @98.75(total $9875), if I sold at same day, I would receive $9425. So I had 4.6% paper lost in 1stday. If I buy back day 2, I will pay around $98.5 again.

3. The Est. Taxable Equivalent Yield: even based on 35% tax rate, I still think their number is too high? Or I miss something? Because I couldn’t get their number by using formula other websites provided

I have traded a lot of mutual funds (include bond funds) from fidelity in past several years, it is a very good company. But I never buy Corporate or muni bonds from it before, is it a good place to buy bonds?