I hope this image is pretty self explanatory, yeah I know it's rough, did it real quick with the kids hanging on me... Top view looking down and a side view...
Basically you make a box around the fan/light/thermostat, with an opening on each end (screened over) this box has a solid bottom to stop heat from going down, as well as a front wall to stop heat form going forward... What this does is force all the air to blow across the light bulb and also across the thermostat... Ideally the thermostat should be mounted a few inches away from the light, with the bottom metal part of the thermostat facing the light... Fan should run 24/7, if you look at the light blue arrows they show air flow, this will create a constant swirl of air in the incubator and equalize temps throughout, between the fan running 24/7 and the fact the light is in a box, almost all 'hot' spots will be eliminated... Do make sure there is some space around the light, you don't want to start fires, I highly recommend a porcelain light fixture over what you have...
And maybe this will help, this is a picture of my cheap hatcher one night build, it uses basically the same design, but a little fancier basically just knocked together a box around the light/fan/thermo out of sheet metal...
This is perfect!!! I totally understand, and I think I can do it myself!!! (although, DH is probably going to want to help) Anyway, yes, your image is very self-explanatory and your pictures help as well. Thank you so much for this!!!