You have found the total current when you short out any two voltage sources, but you also need the current going the other branches of the circuit.
your i_1 is i11, your i_2 is i22 in the diagrams above.
After you have solved the circuit for each source individually you can add together the currents of each branch to get the total current of the final circuit with all sources.
So the current through V1 with all sources would be i11+i21+i31. You can then use the total current to find any voltage drops you need.
I it is not possible, with out solving the circuit in some fashion to know the directions of current you are taking about in your questions. It would be a good idea to include a diagram like on fo the below or add an up/down, left/right annotation to your current where appropriate.
You can draw your current arrows in any direction you want, if the current is actually flowing in the opposite direction of your arrow then then it will just end up being a negative current in your solution.