Why is my circuit nodal analysis not giving the correct I_sc value?

[theBEAST]

Homework Statement

The Attempt at a Solution

Essentially I am having trouble with solving for I_sc when I remove the load and replace it with a wire.

I used a super node at 1 and 4 and also in my diagram I have defined the currents with directional arrows. I have been on this question for a long time and cannot get the correct answer which is I_sc = 8mA. I know it is wrong because I plugged it into wolfram alpha and ended up with the results as seen below.

From KCL:

Where V1=a, V2=b, V3=c, I_sc=x and solving it gets:

 

[NascentOxygen]

V₂ = 0, because node 2 is shorted to ground.