Well I think I listened to this after you have made some adjustments? I think it's a really great tune, very cool chord changes, melody, and lyrics. So it's hard to ask for more than that!
If this were my song, I'd completely nuke that harmonica. Maybe just keep the "reggaeish backbeat" hits, those kind of fit. If you like the line it plays, maybe another instrument. I could hear some B3 on this!
And, if you say you've already brought the vocals up, then OK but I'd say bring 'em up again. I don't think the listener would be depressed at all - your voice has life experience in it, and that's cool.
nice one!
cheers,
-Tom