I assume the dimensions are interior and before acoustic treatment? The booth does feel a bit constricted, but since I imagine the brick walls are already in place, so moving them could be considered complicated. That small it's going to need to be very absorbent to stop it sounding 'boxy' I think the computer should be outside the booth entirely, so cable traps both from control room (ha, ha) and booth. Is that a window through the door? You'll both be sitting a right angles to it, with mic stand and lectern (and swivel chair- you don't want to force your voice talent to stand up for three hours continuously, even if it is better for breathing and voice production) in the booth, and a shelf for keyboard, mouse, screen and interface (and probably a headphone amp. and another copy of the script) and another chair - you don't thing I'm going to stand either, with no technical advantage, and I get a cushion.
Ventilation? A chicane, lined with something sound absorbent, so that sound is lost at each reflection. Diffuse the airflow so it cant hit the microphone with any force. Standard electronic whisper fan, run half power to reduce noise still further. We don't care about rumble below 50Hz, for voice work, which makes everything easier.