.. I guess I really just gave you some links which you probably would have found yourself - as I said, I didn't think I could add much more to the scenario you already mentioned.

But I kept coming back to your question -

. There are places over 100 miles from shore that are quite shallow, on the order of 100-200 feet. Would this make a tsunami higher or would the very long gradual decrease in ocean depth slow the wave through friction, causing it to lose energy?

That does some uncommon CTTOI (come to think of it) - really shallow, so far offshore. Maybe then the wave would reach its maximum height much further away from the shoreline than in many other instances (to conserve energy flux, as explained in the links in my previous post). The question is then as you say whether the seabed in the remaining distance to shore, is going to dissipate energy through friction, to a degree enough to collapse the tsunami before it reaches the shore. The simulations apparently show that is would not lose that much energy, and the dispute over the predictions seems to be based only on whether an island would collapse into the sea in one huge gulp, or if it would disintegrate more slowly over time. Maybe that means that the wave energy is transported more through surface motion than underwater (think of how top-heavy a tsuanmi looks in snapshot). The velocity, and kinetic energy could be 'based' in a non-turbulent area away from the seabed and closer up towards a sort of instantaneous 'water level'.

That's just guessing though, either a geologist could help you more, or a more experienced and capable physicist than me.