Wow. The music is great, you did an excellent job mixing the guitars and drums.
The highest peak in the spectrum riches -8 dB, so you can Amplify 1.3 without going to the clipping zone, but to be on the safe side 1.2 should be good enough. That would make your track sound louder which is great for people listening with regular stereo speakers on their desktops or laptop computers.

I really like the theme of the vocals (good story), it goes well with the music; but I think it’d sound better if you place some of the samples before the music starts and then where the breaks are, for instance at the 1:36 to 1:55 mark, also at the 2:38 to 3:12 mark (I know you already have samples there, I’m just pointing out where the breaks are)
The reason I say it would be better to place the samples in the beginning and at the breaks, is because I feel that the vocals take away the attention from your soloing and sounds a little crowded in some parts.
The ending is a little unexpected, maybe fading out from the 4:00 mark would do the trick.

That is just my personal opinion Dave, I wish you the best of lucks.