Great detailed post!

For others who have wondered if the Abbey is worth the trip, it absolutely is. We went by train both ways this summer (couldn't spend a full day round trip). I had hoped to do the OP's exact trip but it didn't work out that way.

The view as you walk from the train station down to the old little town with the Abbey looms above you is impressive. You really get a sense for how big it is. There are a few paths to get up the hill, very quaint steps carved into the hill and we rarely saw people as we walked up.

The Abbey museum was not really my thing, but when you leave the museum and go through the rest of the Abbey, it's spectacular. The views of the river and valley are gorgeous. The old library makes you feel like you've traveled back in time, and the church/chapel area maybe has more gold than any church or cathedral I've seen in Europe.

I've been to Vienna (which I enjoy quite a bit) and the surrounding area a few times but that Melk trip would probably be my highest recommendation now for anyone visiting the area.