I dont think you can merge arrow stacks, however if you equip 2/10 arrows and have arrow supplies, i think your archer in battle will get 10 arrows but im not 100% sure.
2 skulls missions. Well. This is a tough one. The problem is that as with many other things this depends 99% on context. Namely which build you went with. If you make one build, you can take Orc contract with 3 skulls, but youll struggle with 2 skulls goblins. I dont think there is a particularly good answer to that question in general. The closest i can give you is unless you messed up leveling completely you can surely take 2 skulls missions between level 3-5 provided that you have full 12 people party.
Ofc this also depend on difficulty level as missions scale up in difficultly pretty insanely.
