Regarding cubic feet: do all "cubic feet" spells have to be in a cube, or can the caster choose different shapes, such as a 10x10x1' plane instead of a 4.64x4.64x4.64' cube? There are a lot of spells that use cubic feet as a measurement, both in this spell list and outside of it.
In general, if the spell specifies dimensions, then I assume those are the limit. E.g. Cracks Call is a 10x10x10' area, so it's not going to exceed 10' in any linear dimension. But if specifies a volume like 100 cubic feet for Stone/Earth/Mud, I assume it can be any shape.
Shatter spell: since the range is touch, does the caster take the A critical? Since the spell is "F" type, no resistance rolls are allowed unless the object is metal, correct?
I'm not sure of the intention on the caster taking the critical, but it seems a little odd to me. I probably would not have them take it.
The Mystic's version of this spell has a 10' range. In that case, I would say the caster will be affected if within the blast. You could use that version instead.
Type F spells ("force") always permit a resistance roll. That's basically the meaning of type F. Metal objects get a +30 bonus for this particular spell as noted in the spell description. But normal, non-magical items not being held generally don't get resistance rolls or would be treated as level 1. Magic items could use their level. Items being used by a person, even non-magical ones, would use that person's level.
Break Solid spell: Is this intended to have a range of 100 inches, or is that a typo? All the other spells are touch or 100 feet. The obvious application is to cast this on a foe's weapon, and it seems like a very powerful spell used in this manner. Is this intended?
I assume it's supposed to be 100'. That's consistent with the Mystic's version of the same spell. As above, the item would get a RR based on its wielder's level; magic items would get a bonus to that. I don't think it's overpowered given its level.
Work Magic Cloth spell: I know there are a few spells that do this, but can anyone give some examples of magical cloth? I'm drawing a blank on magic cloth used in any fantasy literature that I've read/watched. (Excepting magic carpets, but I'm not sure that the cloth itself is magical in their case.)
Perhaps silk woven by giant spiders? Or magical types of spiders like multi-spiders? The hides of some creatures might be considered cloth for these purposes too, e.g. deerskin is leather but it's light enough that what you make out of it is going to be considered clothing and not armor.
