That was well deserved toxo. You did a great job using your skills and intuition. You also did a bang up job of explaining how you did it. I actually ordered the thermostat kit that you used and tried it out. This is what got me interested in electronics. After my many alterations to the circuit, i was able to design and build my own to suit my incubator needs. I am now on my way to being an electronics engineer. So, i owe you a debt of gratitude for your free willingness to share. Thanks and congrads.
So I would suggest this small change. Use the Peltier cooler instead of a bulb. These Peltiers can heat to 50F above ambient temperature (ie, room is 70F, these can heat to 120F) or they can cool to 20 below ambient (ie room is 70F, these can cool to 50F).
They are used in car coolers, cpu (computer chip) coolers, and I've seen them in some lowend water coolers.
I would have used the Peltiers for the heat, they could easily be kept at the right temp. Peltiers are hardy too, I've never seen one burn out. I would add some warning system, just in case, though.
Even without that, excellent job, great incubator!