I'd arrive by 7, just so you can cut out one cause of anxiety. As for dealing with the anxiety, I'm a recovered fearful flier and here's what helped/helps:
1. If you're a coffee drinker, definitely have some so you won't get the withdrawal headache, but cut down.
2. Let yourself eat comfort food before/during. Even if you want to eat healthy in WDW (sad! lol) the flight is the time to allow yourself the candy or whatever.
3. If there's a friendly-looking flight attendant, feel free to ask on the way onto the plane "How does the flight look for today? I'm an anxious flier and it helps me to know if there's going to be lots of turbulence." That person, ideally, reassures you but also, you're a known commodity to the crew.
4. Remember it's absolutely the safest way to travel! And that the pilots/flight attendants also have families they want to get home to. They're not taking chances.
5. Don't go for alcohol or any tranquilizers (alcohol will amplify anxiety/fear in the wrong moments, and it's unpredictable. Tranquilizers should only be used if you absolutely know how they work in you. Being confused or incoherent isn't going to help anything and may make it worse.
6. IF you're spiritual or religious, you can post here or on something like social media that you're about to take off and would appreciate some prayers of comfort. For whatever reason, this really helped me a lot.
7. Download a guided meditation or relaxing music. My daughter swears by one of her "comfort movies" (in her case, Ocean's Eleven or Mama Mia, but that's her lol)
8. Bring something like a blanket you love or wear your absolute favorite comfort clothes--you can change in Orlando!
9. Never try to "read" the faces of the crew. If they look grumpy or stressed, chances are it has to do with anything other than the safety of the flight. They forgot their lunch or don't like that guy in first class or their kid was rude to them. They're not frowning because something terrible is going to happen.
10. Remember that you are on vacation the minute you step on that plane, and relax. You'll get there.
Not comprehensive, but maybe something you can use? ENJOY YOUR TRIP.