Very cool prod, I definitly love the sound design and progression. I aint the first to point it out but you gotta work on that lead, I dont think you should delete it altogether (as you suggested below) but at least put it in the right scale. Look at your chords and bass lines, take the notes and put them in a scale finder. Try to only use the notes from that scale in your melodies.
That link looks pretty useful, I'll give it a proper look once I'm back home, and will try to see if I can get that lead to sound a little more in tune. Thanks a lot for the feedback :)
Once you get a better grip of scales you can get out of your current scale for some interesting effects, but to play safe you should try to stick to a single scale.