DC Output Voltage of BJT Differential Amplifier with Active Load
The DC output voltage of a differential pair isn't a particularly useful figure. As with any input offset voltage from mismatch the output will rail one way or the other.

The simple answer is that all your PNPs are matched and your NPNs are matched. 

So, in the left-hand branch you have an extra \$2I_b\$ from your current mirror.

The left NPN has a \$V_{be}\$ which is based on this extra \$2I_b\$.  The right NPN has the same Vbe but see's 2Ib less collector current than the other branch. So the right NPN saturates trying to pull the same current as the left NPN.