That axle truss is not going to help your death wobble at all. I'm not saying you don't need it, it would help with the axle's strength for sure. You need to jack up the truck and get both front tires off the ground. Then, grab the top of the tire and try to push and pull on it. If you have a significant amount of play, or can feel "slop" in the tire, you have bad bearings somewhere. Either in the wheel bearings, or the steering truinion bearings.
Then, grab the tire and move it like you were steering it from inside the cab. Anything that has a lot of play or is worn out should show up pretty easy. Replacing a bunch of parts with no plan is a bad idea........remember this simple rule always........Don't fix the symptom, fix the damn problem! Find out what is wrong and fix it.
Also, check your steering stabilizer. It should be tight with almost no play. That said, steering stabilizers help to hide steering problems and in a perfect world, you wouldn't need one. Unfortunately with big off road tires that are not truly round, you need a steering stabilizer. That brings up another thing, rotate your tires and see if your death wobble goes away. You may just have a bad, unbalanced tire. good luck.