Glad to hear you are coming back. To answer your questions:
No abilites are "needed" for Lancer in particular. But you will find that there are useful abilities if you are playing solo.
Lancer is good for "the theoretical Engame" so far. DD is always a nice addition to any party.
Gearing Focus ='s Proper Rank/Class requirements. Unless you don't mind a large stat penalty.
Not sure how Lindblum is doing, but Rabanastre is still doing great. Some days are slow. But most days are full.
Hope that helps.