I agree with the suggestion above that you try another CM as they often will provide different answers.
But I also would encourage you not to stress too much over this. If 4:30 is the latest you can get, go with the flow. Take your afternoon break a little earlier, eat at 4:30 and then hit some rides before the show. This is actually a very good time for rides as many people are trying to dine at 5:30-7:00 so the lines can be substantially shorter. Really, an hour or so doesn't make that much difference.
In our experience, we find that by having an early morning breakfast (7-7:30) and a late morning lunch (11:30 or so) we are definately ready for dinner by 4:30-5:00!
Planning a trip, for me, is at least half the fun of our vacation so I can appreciate your wanting everything perfect. You set out a basic plan - know which parks to hit and when - set your PS times - get the best prices you can on hotels and park passes - then you go forth and enjoy. Sometimes the best things about a trip are the little unplanned surprises. You'll have a wonderful time because after all in the grand scheme of things, IT'S DISNEY WORLD - how could life get any better?