I didn't see Luke's actions as a 'leap of faith'. It was an act of desperation and defiance. It was his only choice besides taking Vader up on his offer- which he would never do. Yoda and Ben warn him emphatically not to go. Ben tells him he won't be there to bail him out if he gets in dire straits- which to the audience remembering the 'use the Force' scene from ANH clearly brings home the point that Luke is alone, without Ben/the Force to guide him. Ben even tells him if he chooses to face Vader, he will do it ALONE. Ben acknowledges that the Force is indeed with him, but Luke cannot control it. There is no reassurance from his teachers- quite the contrary. All of these warnings come to fruition when Vader has beaten him, crushed what he believed his father was, called out Ben as a liar, and tempts him with Galactic rule. Luke is at rock bottom. He doesn't look within himself or has some internal revelation or a moment of clarity like he did on Hoth in the Wampa cave. If he reflects on anything related to the Force, it's the dark omen he experienced on Dagobah in the tree. Luke is at the crossroads to where that omen is face-to-face with a harsh reality and when Vader says 'it is your destiny...it's the only way,' Luke defiantly takes the plunge into the abyss. I don't like this action to be akin to a suicide attempt, it really wasn't that. He chose to sacrifice himself rather than accept the so-called destiny Vader has tempted him with which he himself witnessed in that tree. Here's a good rule-of-thumb if you don't understand a subtext in the SW movies, listen to John Williams' score. He gave that moment when Luke lets go a fanfare- tragic in tone, but a fanfare nonetheless. Luke made a bold move. Heroic.