The acceptance modifier of -1000 seems to be a lie but also truth. If you're equivalent in power (overall) it'll be there stating they wish to stay independent. If they are pathetic or inferior (overall) that modifier (for the most part) has been removed. It has no effect on the actual vassal contact as the vassal contact is based on your power to them, distance, and everything that's in the contract. So, personally, ignore that modifier and see if they'll accept your terms or not.
Now, if you're asking to be the vassal, of course it'll be there because certain authorities and governing ethics do not like having vassals. Most notably Democratic authorities with Egalitarian or Xenophile ethics. Those don't like vassals but, seem to like Bulwark Vassals. . . Had a game going where they proposed me becoming a bulwark
Edit: in regards to the -22 from terms, that is referring to your default terms. Oppressive, Balanced, or Benevolent. Each have their own setup and different authorities and ethics have their preferred terms