I’m outdoors so can’t go into detail but some inputs:

1) theoretically you can I suppose, but it depends on your clear time ofcourse. If you’ve experienced GW, you’d probably already know that things never go as planned so just focus on finishing the tokens before finals starts if you can.

2) Can’t remember

3) Other than Wind and Earth, the other grids will only consistently cap if you have ULB Opus, or are in specific situations (enmity for Dark and Fire). Else, like you say, your characters (or your class lul LJ) will be carrying themselves. After this, it ain’t strictly “M2” anymore

You may be suffering from lack of damage cap, though I doubt this is your problem yet. Other than Opus Seraphic Astral, assuming they aren’t in your grid yet here are notables:

Rotb Progression weapon

Fire: +Rotb Gun, Cosmic Sword if you can fit another sword (Baha or Ushumgal)

Water: pretty full, Wamdus spear maybe...

Earth: max +2 ancient perseus and rotb spear, else Caim grid

Wind: should cap handily, slot in rotb spear or Ewiyar beaks (not really core)

Light: 1 meta bow for short fights, cosmic sword... the 2 meta spear grid exists but suffers at lower hp

Dark: Avatar spines? For non-enmity, Avatar harp and 1-2 fediel spines