Défence question

There is no way to answer this beyond saying that it all depends upon the location of your planets and the people in that "neighborhood"

Set up some defense. And see how it goes. If you get attacked, up the defense till it stops.

it depends on the uni and how many sats are there generally that much res you shouldn't need more then about 5k rl and a couple hundred mixed of others and around 20 to 25 plasma just as deterrent to solo rip hits