Help???

Generally speaking, I think he seems like a pretty good character. I have a couple questions about his appearance though

Dark brown hair with natural lighter brown streaks here and there. He has a silver, almost white, stripe in his hair

Is there some kind of significance to having the silver streak in his hair? Is this something that occurs naturally in his world or is there otherwise some kind of explanation? It's just a little weird to me that a 23 year old would have that.

Hazel eyes with specks of silver and green

I'm kinda having similar thoughts about his eye colour as well. This doesn't really sound like a real thing (or maybe I'm just not picturing it right).

(I didn't really get a chance to read over the rest of his page, but I'll try to get to it later if I can).

I mean honestly, he's looking really good so far. I agree with the physical appearance stuff, so you might want to look into that (but you already are so).
He feels pretty complete as a character, but of course, as you figure out more details, he could always use those.
I'm mostly curious about the big black dogs thing. Is there a reason for him disliking them so much?

That's valid. Some people do have irrational dislikes and fears. So in that case, it may be a good idea to clarify it's irrational and not because of some sort of trauma.