I've got a similar setup. I'm thinking airbags will help with the bounce, but may try adding a washer as per above.
One thing to note is that your tongue weight is a bit more than the weight added to the truck. I weighed my trailer tongue, not hooked up, just the tongue on the scale, at 1050 (480KGs) but find that all hooked up, it only adds about 800lbs to the truck with some of the tongue weight transferred to the trailer.
So where you show your tongue weight around 620, you may find if you just weigh the tongue, it is 800 or so. But 1K basrs still sounds right for your setup.
