You may be in shape physically to handle this schedule, but if you are depending on the WDW transportation system, you're going to have problems.
For instance, you're going to have a difficult time watching BatB at 12:15 pm, which is a half-hour show, catch the Friendship boat to Epcot, which may not be until 1 pm, and make it to Epcot in time to catch the British Invasion at 2 pm. The boat rides will take anywhere from 30-45 minutes, unless you get off and speed walk, then you have to go through security, and hope for the best.
You might consider doing some of the other things at Epcot on your agenda and catching a later British Invasion at 3:30, but then I don't think you're allowing yourself enough time to take two monorails to the MK and get to the castle by 5:30 pm. I'd drop the Living Seas, or Epcot all together that day, and go straight from the Studios to the Magic Kingdom by bus.
In case you don't think we've tried something like this before, Linda and I were on Main Street one night watching an 8 pm running of SpectroMagic. As soon as it was over we hustled out to the express monorail and got off at the T&TC, switched to the Epcot monorail, which just happened to be in the station, and went to Epcot. We ran into the park, and got a place to see the 9 pm Illuminations with 10 minutes to spare! It was fun, but I wouldn't make a habit of it.
As always, your mileage may vary!