also is there any way i can get my vassals to make peace with an enemy when i make peace with them?
When you make peace, all of your vassals who are currently at war with that empire, should also become at peace with them. If it's not working that way, posting example or details would be helpful.
The only thing close to what your asking is, if you are a vassal of someone, go to war to grab another county, your liege (possibly also your ally or liege's ally) also goes to war with that county. You force-vassalize that county, but it's still at war with your liege. The only way out I've found, is to give that county a few gold (4 or 5) at the start of each month (if it has no gold), and hope it settles with your liege for that gold during the month.
im the byzantine empire and i have a few provinces in persia, russia and hungary that i want to get rid of but i think it would take to long and cost to much rep if i took them from my vassals and gave them to one i have a claim on the attack him.
The further away from your Capital, or the Vassals owning Counties in Kingdom's and Duchy's natural area of influence that you don't have the title to, will tend to revolt/declare independence eventually. The only way i know of, to re-distribute Counties and titles, is during a revolt (or by revoking titles, with all the bad things that go along with it).