First off Disney can and does remove the $10pp charge for missed ADRs if you call them (or even on check-in) let them know you missed it because of a flight delay. Better if you can call enroute and let the place know but that isn't always possible.
Second, 3 hours is reasonable. Because
o get off the plane at MCO
o make it from the Gates, to lower level of Terminal B
o scan in @DME wait for a bus to load and leave
o 45 minutes to WDW plus what ever random stops you make before CS
o check-in/pick-up
o drop carry-on off at the bell or go to your room
o wait for MK bus
o get through park bag check
o get through turnstiles/gate
o go to your destination
All the steps involved are pretty fast 10-15 minutes (except for the drive which is about 45).
Every time there is a post like this someone says "Oh I got from my plane to the first ride on SpaceM in an hour and 22 minutes" (or some incredibly short time.) It's like driving in town, if you hit all the lights and everything is with you it's only a 10 minute drive, but don't count on it.
On arrival day I mostly just do CS, or if I do want TS, I do walk up/same day ADR. You can get walkup TS if you know when and where. You can look in
MDE, or call 407-WDW-DINE or go see a concierge and ask who has TS ADRs left for the day.
Where you are coming from and heading to I would suggest, The Wave, or Kona, as my first two choices for walk-up. The Plaza would be a good choice too, but I would try for an ADR day of arrival (likely though MDE on while I was traveling on DME).