When searching for flights, ensure Spirit Airlines is excluded.
Unless there's a massive price difference, just fly Southwest if you have luggage. In over a decade, it's rare that some other airline is a lot cheaper. Most of them are at price parity or more expensive with luggage. In any case, at this point everyone in the US knows you'll get charged for luggage with most airlines and account for it when searching.
Food: Just don't. They give crappy snacks on planes. Just bring a few along with you. Or even buy them at the airport.
Insurance: Go to https://www.insuremytrip.com/ and get it yourself. Ignore whatever airlines offer you.
Seat selection: Don't bother with it too much. Also, nice that Southwest doesn't let you pick seats.
Priority boarding: Why...? I'd rather sit in the airport than in a cramped seat in the plane. And I've had bad experiences where they've turned the air conditioning off in the plane during boarding and I start feeling sick.
Compared to when I was a kid, flying is much cheaper now (inflation adjusted).