Just watched all your videos on Youtube.
Dude, I'm gonna give you the most honest advice out of anyone so far. And please read the whole thing, because, as you'll see, there's good news at the end.
First off, your covers of Dream Theater and LaBrie's style are not good. Some, like the Asylum City one, are laughably bad. James' voice is very unique, and does not lend well to being mimicked. And your range is not suitable for his at all. Secondly, do NOT imitate James' mannerisms. They look funny enough coming from him. Coming from someone that can't quite pull off his voice makes it even worse.
Now, here's the good news. You're actually a good singer, and I can show you why:
https://www.youtube.com/user/NickySpanjaards#p/u/4/rLUWaDtgQRsYour vocals here are pretty damn good, and I can really hear why you're the singer of the band! Your cover of Symphony of Destruction is also not too shabby.
So I'd say, stick with the lower stuff, and keep at it. And find a new hero. LaBrie's a great singer at all, but even he has a hard enough time with the higher notes-- and his voice is made for it.
You're not a wailer, but you're good. Stick with that real heavy, lower register shit and you'll do fine. Or find some way to work on your pitch, to keep your control from falling out when you go higher. But your gods should be Barlow, Hetfield, that dude from Type-O, older Ray Alder, etc. Not LaBrie and Dickenson.