Great job. Personally I think Russell's timbre is better matched and irreplaceable for the Symphony X songs (obviously, because they wrote them for him), and I think your voice is a more natural fit for Dream Theater-type stuff, which you pull off excellently. No harm in that; just different voices have different timbres.
You still do the song justice here, but just one observation from something I noticed a few times:
Every voice has certain keys that it fits into best and in the verse, which you did in the original key, there seems to be one problematic note that pops up a few times.
On the syllable “fec” in “inFECting one and all” in the first verse, you seem to be a little flat on that C. You can certainly hit the note but when you come from underneath in this case, you don’t quite get all the way up there; listen to how Russell really bends up there. The same place the second time in the first verse, on “rise” in “some will RISE and some will fall,” also seems to be a little flat.
In the same part of the next verse, in “ne” from “NEver losing sight,” you seem to be straying into C sharp a little bit, which is an accidental out of the key of the verse (D dorian), instead of the original C, so just watch that there.
I might be wrong on this (I don’t have perfect pitch or anything), and I can’t sing at all myself, but I thought I would just point that little detail out. At this point it's not really about skill; it's really just an issue of doing lots and lots of takes and getting the perfect one for each verse where that one note really shines. Otherwise, great job.