I haven't played Aurora 4x for few years and not I started new. I run into new problem in every game.
Civilian ships will move so many colonist and Protection Required will sky rocket. Example in Alpha Centauri Protection need is 26 650 / 813. No matter how many ships or troops I move there I can't lower it. Alpha Centauri have spaceport and I am terraforming it too. It can support 67 012m people and have 70 428m, but I think infrastructure is not the problem.
How to lower unrest? I can't build enough ships to fulfil my colonies protection.
Maybe your population is much larger than the support that planet can house. This produce the unrest. And a lot of deaths.
I think you should move some colonist elsewhere.
You can also stop the civilians bring there new people.
In the Economics window, Civilian/Flags tab, at the top of the window, you can decide if the planet is a source or a destination of colonists, or if it is a stable population.
Buy, really have you
70 billion people on the planet??!!
How many people have you started the game?