> Fruit only for breakfast. Lots of coffee in between, to give me energy.

As others have suggested, eat protein at breakfast and a small portion at
the morning break.  Limit coffee to one or two cups.  In the end, coffee
undermines energy.  Try caffeinated green tea as a substitute and means of
weaning off of coffee.

>The protein component at lunch seems to cause some digestive difficulty
(feels like a brick in the stomach for > hours afterwards). Meat at dinner
is not a problem.

Eat a smaller portion of protein at lunch (you may be starving from avoiding
protein all morning).

You may want to try a proetolytic enzyme supplement at lunch to see if that
helps.

Rob