Lando's "sin" was selfishness. The only way to fully redeem himself for that is selflessness. The points you mentioned demonstrate some selflessness, yes. But keep in mind the magnitude of his betrayal. Han would never have been frozen or taken to Jabba's "nasty palace" if Lando had made a stand...or even warned him in some way...C-3PO was blasted to pieces, Leia, Chewie, Han and Luke were all lucky they didn't get killed. And if they HAD been killed, there'd be no Vader redemption and the galaxy would never have broken the Emperor's grip.

What he did was baaaadddd....

If more emphasis was placed on Lando leading and orchestrating the rescue to try to right his wrong, maybe it could be justified. But in the movie more emphasis was placed on Luke's part in that. In my opinion, Lando didn't do enough on screen to balance out his misdeeds. And of course self-sacrifice is the ultimate expression of selflessness.