Hi,

Not aware of the use of Tempera paints for modeling but I don't think they would harm your airbrush, particularly if your AB has Teflon seals. You would have to thin it - water maybe - but, if to be used on plastic I would be concerned about adhesion. Let us know how it works!!

Yes, it can't harm your airbrush but I've had problems thinning the stuff, it seems to want not to mix that well the times I've tried to airbrush it. Please let us know how it goes.

The only danger to an airbrush is in how fast it dries. I find some acrylics dry so fast that you must be diligent in cleaning immediately after use.  I don't know how difficult it is to clean tempera, but some acrylics are very hard to clean once they are dry, and you have to disassemble airbrush and clean thoroughly.