Life is game, you gotta enjoy the journey.
Life may knock you down sometimes. Its up to you if you stand up and live your life to the fullest.
Yes. Lando fulfilled his requirement to reveal RM. You don't need him after that.
Even if you lost ground battle but won space battle and Empire has after captured that leader you still resolved the mission earlier and get that reward later (end of command phase).
One check though: you state "I did not move in an extra leader for the combat"... since Lando is present, you cannot send in another leader at start of battle. You can only do so when you dont have a leader with tactics present.