I got tax rate 58%, morale 100% with 15.00 billion pop. PQ 23, 2 VCRs. That's the result of 1 fully upraded Morale Starbase + Planetary Adaption

. Some other techs that improve morale...
It was a crisis that all planets in some sectors got quality of 5. I built weather controls, terra formings, improve PQ to 12-13. Now, total pop. were about 800 bill. Morale 99%. Income...7000, tax rate 58%
Thala's homeworld joined my empire, it has 24 bill pop, morale about 96% (I built almost all slots with VCRs, aboult 10-15 VCRs). All others have 10%.
Another planet with 100% morale and 22.00 pop with only 3-5 VCR (no bonuses)
300% farming bonus is totally useless, or dangerous. With a fully upraded farm (and a food distribution), max pop. is 52.00 bill. I don't know how to deal with it. I think star dock should remove it, and make another better bonus (say 300% morale bonus)