The Ker bomber is overpowered. It's superior to other heavy bomber options while being less OP expensive. As an example, I'll compare it to the Trident.
Ker:
18 OP cost
2 fighters per wing
20 second refit time
750 hull integrity
50 armor
1000 capacity omni shield
150 speed
Payload: 2 Cluster Torpedoes dealing a total of 300*22 = 6600 HE damage
Other Weapons: Burst EMP Emitter, capable of instantly disabling unshielded interceptor wings.
Trident:
25 OP cost
2 fighters per wing
20 second refit time
500 hull integrity
25 armor
500 capacity omni shield
130 speed
Payload: 4 Atropos Torpedoes dealing a total of 1000*4 = 4000 HE damage
Other Weapons: Nothing.
The Ker has almost twice as much total shield/armor/hull, is faster, is much more capable of defending itself, and delivers a heavier payload for 7 less OP. The lower per-shot damage is more than made up for by the higher total damage and the Ker's other advantages. In testing vs the low-tech practice target, a.Ker wing's payload of 2 Cluster Torpedoes punches through 1750 armor about as effectively as a Trident wing's payload of 4 Atropos Torpedoes, so it's not lacking for armor penetration.
I'd recommend increasing the Ker's OP cost up to about 25 and making it more fragile than the Trident, while leaving its speed and EMP emitter alone. Maybe even bump it up to 160 speed to keep it very distinct.