I don't particularly think much of VDD. He has his fruit however a range fight is still easily ussop's territory. Anything that VDD could throw at ussop would IMO be stopped by one of his shots rather early. On the other hand, there is little VDD can do to defend from ussop. I guess ussop would have trouble if something sufficiently large enough is thrown at him however that would be a rather extreme scenario. Ussop right now has the sheer firepower to put a rather large crater on the ground, VDD would need something more than a few stories high for ussop to not be able to handle it with his own shots at a distance. That is, assuming the fight gets to be that long.
Van der Decken showed very little combat ability. With Usopp's versatile arsenal, I'd say Usopp takes out Van der Decken relatively easily.
I don't know, but it seems that I'm the only one who believes in Van der Dekken.
Seriously, the guy showed to be quiet good fits in tanking as he managed to take Luffy's Haki coated Jet Stamp and then managed to get back to his actions rather fast, but prefered to use Noah, then fight directly with Luffy. He also managed to take a slice with quite a big axe and fainted only because he fell and hit his head.
Talking about his confrontation with Usopp... Seriously what can Usopp do against like tons of things he can throw at him? The only thing Dekken needs is to touch Usopp and considering he doesn't know about Dekken's ability... I don't see any posibility for Usopp to defend himself from like 100 of arrows or knives from all directions and manage to defend himself non-stop from tons of things that Dekken can throw at him that lie in Grey Terminal.
Well, for one thing VVD attacks do not come from all directions, he does not have that level of control. His attacks come from one direction and in a straight line for that matter. As for the things VDD can throw, the issue would be that it is merely only junk. I guess there would be a benefit to throwing it but what does it mean for ussop? Ussop was able to take insanely severe amounts of damage as a normal human, he even survived absurd falls, being hit by a 4 ton thingy and a number of other things. Ussop is more likely to get defeated by an infection due to being cut by garbage days after the fight than by the actual trash lol. IMO ussop has the sheer firepower to hold the stuff VDD can throw at him at bay. He can use his explosive greens to stop the larger things or create entire forests and whatnot to get in the way of more things which is more than enough to stop VDD. And then, what can VDD do against ussp? He never showed any insane strength nor power, how would he defend? Ussop has at least 2 nukes, carnivorous plants, he can grow forests and the things he can do with the seeds seems neverending at least. VDD has no real defense against anything really.