precipitato, what are you referencing when you say that you believe there should be something else too? Something more to the pedaling equation or interpretively? I'll gladly share my own thoughts once I know what you are seeking more information on.
One thing to be mindful of is that that opening portion in repeated chords and octaves is marked "lamentoso". I think that even after it get's rolling and is mf, ff, etc. that it still needs to maintain a quality beyond "fiery". It's the wails of the damned, who are most assuredly in the fires (!), but I would ere on the side of pathetic... at least at first. Once you get to the rotary octaves, etc. that is really where you want to open up and relish in the terror... Build your climaxes, don't kick the heck out of the piano!
As for the end, I would NOT advise that you use Mazeppa fingerings. Use "consecutive third" fingerings.... Although I would be tempted to do the same in Mazeppa (yes, go against Liszt's fingers), I would be remiss to discuss that passage at length here. I kindly suggest others not piggy back on this portion of my post. In any event, this is a totally different sound world and texture, more gossamer-like, quieter, etc. If you would like my specific fingers I will give them to you in a future post... for now just try what lies under the hand..... And make sure the passage of the arm from octave to intervals and back again is carefully choreographed for maximum poise, ease, and beauty.