2) Is there any way to reduce colony maintenance? Owning more than 4 planets bleeds me dry.
Try building market centers and other economic buildings. I try to counter maintaince costs by not teching up structures too quickly (maintiance costs of buildings ussually increase as they advance, Thalans are a weird exception), and by building plenty of market centers and other structures (the Yor can't do this without tech trading, so that could be your problem).
Any way, you might want to take a look at this:TA 101
I wrote the guide to hopefully reduce frustration of those who are playing TA for the first time by providing ideas of what one could do. It assumes that you already know how to play DA (Dark Avatar, the previous expansion), but if you are new, it shouldn't be any problem answering your questions.