"Also if I roll for crits after a failed DFA, shouldn't I also roll for them after falls resulting from displacement to a hex two or more levels lower than I was displaced from?"
With Weak Legs, you apply damage even on a successful DFA.
Rolling for crits on a successful DFA is obvious from the quirk description I was asking about rolling for crits after an
unsuccessful DFA (when you don't take the damage to the legs specifically, only fall damage "[...]as if it [the attacking 'Mech] had fallen 2 levels onto its back[...]" - see the last sentence on p. 37 BMM (or under Falls on p. 150 TW, where it is worded slightly differently, but the meaning is essentially the same), and if you roll for crits after an
unsuccessful DFA - should you roll for them in other situations, when you essentially fall from above (as opposed to just "tripping and falling" in a hex the 'Mech was standing in).
From your previous answers I understand, that I roll for leg crits on any DFA (successful or not), but not on falls resulting from other situations. Is it correct?
What about falls caused by damage to a 'Mech attempting DFA applied during Weapons Attack Phase (see Weapon Attack Phase on p. 37 BMM/p. 149 TW)?