The airport will be busy...many people will be doing the exact same thing you are doing to avoid the higher fares.
So....are you going to be able to check your bags at the resort before leaving in the morning? That way, you won't have to do that at the airport and that takes up time.
So...if your ADR is for 8:10, I would get there by 7:50..maybe you'll be able to be seated early. If not, at least you'll be seated pretty close to 8:10. You should plan on being out of Chef Mickeys by 9:15. Then, drive to MCO and let the others off at the departures area, and you return the car. That way, not everyone has to trek from the car rental area. But, be sure you have your boarding pass and ID with you (if you did RAC that morning).
You should be at MCO no less than 90 mins before flight departure if you have already checked those bags at WDW. If you have to check your bags and get boarding passes, then you need to be there the full 2 hrs before departure.
With an 11:45 flight, you should be at MCO by 9:45, not later than 10:15. Which means you have to be on the road by 9:15, at the latest.