Frankly, taken by itself this is meaningless. From the information released, there's nothing that indicates either of the knives belonged to him (this is from the search of his parents' house in PA) or that they've even been in the state of Idaho. The gloves and flashlight don't provide evidence of anything, you can probably find those in most of our houses.
The clothes could be meaningful, if he was dumb enough to keep them and then travel across the country with them. I'm willing to bet he was not. I'm also willing to bet that the knife is in the river in Lewiston, or that it and the murder clothes are buried somewhere south of Moscow. The shovel found in the car makes me suspect the latter a little more, but by itself the shovel also isn't necessarily evidence.
The car is potentially critical. A single drop of victim's blood (better yet, mixed victims' blood) will put the needle in his arm, and the most likely place to find that is in the car. From descriptions of the scene and the apparent process, there are multiple factors that make it very likely that he had blood on his clothes, and if those clothes then went into the car, they could find transfer.
My assumption remains that MPD and FBI have much more than they've released, and that this is going to be a slam dunk. Anything additional that they get from Pennsylvania will just serve to speed the path to the execution chamber, and give multiple ways to convict him if the defense manages to get some evidence suppressed.