I might be overreacting a bit due to external factors. It has been hot and humid in New York City for some time, now. I'll give this another try tomorrow.
Hmm, I probably need to balance the early game defense system a bit better. More time on the scout squadron, more time between enemies appearing., etc. I'll make some changes and get the other issues fixed up and then we can see how it feels after that.
As a stop-gap measure, you could make "Tactical Systems" a guaranteed first-step technology. +2 Combat per turn makes a HUGE difference in the very early game.