HGF as far as the Luke falling in ESB goes, I don't think he used the force to slow his descent there, but he was "sucked" into that pipe. I don't think he had either the presence of mind or the skills at that point to use the force in that way (also why didn't he use it when he falls from that antenna onto the "Falcon"; that looks so painful...). However I do agree with you in theory that it would work.