I have service coming into the home and straight into a cabinet. Inside the cabinet each leg passes through a ct with 200 labeled on it. They then each go in to a lug. Each lug has two slots for incoming and four for outgoing. 3 of the slots on each lug are taken. The wires run to 3 200 amp disconnects and then to my three panels inside the home. I want to add another panel. I know it has to be a 200 amp panel, but want to make sure that it will work. My amp reading on each leg of incoming power is 45 amps. My total running amps on the equipment I am adding to the new panel is 65 amps. Will this work?

An amp reading is a meaningless indicator of demand load.
You need a qualified electrician to come and do a demand load calculation. This will determine if you can add capacity to your already huge service.

I will say, IMO a 600 or 800 amp service is no place for a DIY to be messing.

Also, the CT cabinet is off limits to anyone other than the utility.

If you broke seal to gain access to the CT's, the utility will not be pleased.

Any additions to the electric service must include the utilty to be sure the new panel is metered properly.