You mentioned the trailer bouncing around going down the highway and you hoped the Alaskan plus gear would mellow that out. I am not familiar with that trailer but if it does not have shock absorbers it might still continue to bounce around on uneven roads. You have modified the trailer pretty well, have you considered adding shocks if it does not have them or replacing them with a pair designed for the weight of the trailer plus the Alaskan plus your gear?
By the way, securing the Alaskan to the trailer can be done many ways but all put some strain on the plywood at some point. Using a trailer with no shocks on it would be like removing the shocks from your truck and driving around with the Alaskan in it....not recommended at all!
What about using some angle iron bolted to the deck with the vertical angle towards the camper? Adding some kind of some rubber snubber before you secure the angle iron to the side so some slight cushion is provided when the rig hits uneven, rutted, washouts. Then you can add the turnbuckles to keep it from bouncing out of the angle iron. Put some slats crossways to keep water off the bottom of the camper and a couple ways for water to drain from the angle iron frame and you would be good to go.
The rig looks pretty cool.... I'd consider permanently mounting a couple levels so you can check that BEFORE you disconnect the truck. Having a jack on all four corners then lets you fine tune the rig to LEVEL....Alaskans are very particular about being dead flat level to avoid binding the tracks when the top is being raised/lowered. It also makes your bunk dead flat also so you aren't trying to sleep on a slope...