My question is how much load can my 2 each 6 x 6 pre-treated post handle. I have approximately 1,466 lbs of treated wood as my roof of the pergola and it will be attached to the house the other will be 2 each 6 x 6 post in concrete in the ground. I wanted to hang a swing between the 6 x 6 post (350 lbs max weight). My span between 6 x 6 post is 12 ft center to center. I have 2 x 12 x 20 bolted on each side of the 6 x 6 post. I wanted to hang my swing from that.
The 6x6 and the double 2x12 are sufficient in themselves for your swing. But the 2x12s may not be attached securely enough to the 6x6 posts, and/or the pergola may not be attached securely enough to the house.
Also, once the temporary diagonal cross braces on the 6x6 shown in the photo are removed, there may not be enough lateral stability. If you were to convert the pergola into a roof, and sheathed the roof with plywood, then there would be enough lateral stability assuming the framing is attached securely enough to the house.