1. Allow classes that have Set Trap as a class skill to all have the level bonus to DC like rogue/zhent/harper/assassin have. That would mean adding it to ranger, hexblade, vigilante, liberator, specialist, and maybe another that I missed.
2. Acid blob traps can't be crafted in stock NWN and I don't think they have a recipe for it on Arelith either. Pick a material and allow it to be crafted with the set/craft trap system. Alternatively add a recipe that either A) crafts the precursor material or B) crafts the trap but requires either Set Trap at x skill level or levels in classes that have Set Trap as a class skill. CP could be boosted to keep the numbers low if desired.
Edit - Acid blob traps are separate from acid splash traps. Acid splash traps you can craft with acid flasks, acid blob traps you cannot. I checked on the PGCC really quick to make sure.