Mavericks said:

Indeed, THIS did tessellate. Well, of course it should have been so obvious earlier. But here one moment of questionable participance of Harrison in ROTJ appears: after they turned Han's body into the piece of Carbonized Ice, Lando squatted down and after a brief revision of life gauges, stated that "he's alive". So, if Han survived wasn't it somehow connected to the fact that Ford was viewed as a member of the cast on ROTJ set?

No, the reason Lando declared that Han was alive still is simply to leave the possibility open of having Harrison Ford return to the role. If Harrison Ford declined to appear in the third movie, he was basically already written out of the picture, and if he did decide to return, they could write him back into the story without having to resort to a retcon.