Dcour,
I listened (sounds good) and looked at the waveforms. You just need a limiter/clipper on this. You can stick it directly on your mixbuss as the very last insert, post-fader, or you can bounce the mix so you have an non-limited version (very good idea to do) and then re-import it and just apply the limiter/clipper and bounce that for the master level mix. It’s always a good idea to have both a master level mix and the unadulterated mix. You could also just do a mix like you have (as a 24bit wav file though, obviously), and then do a second mixdown with the limiter/clipper on it (also as a 24bit wav file - you can then make a separate mp3).
Basically, what you have is the normal mixdown. This is like what a mix engineer would send to a mastering engineer (if it had vocals). What you need is a mastered version, or just a master “volume” version that’s as loud as a mastered record. We usually technically call this a “master level” mix. Meaning it’s the mixdown, just turned up to a mastered level with a limiter or clipper. When you "shop" your beats, you want to shop the master level mix. The artist or engineer working with them will later ask for the multitracks (although, mixtape stuff, they might just ask for the non-master level mix.... or they might not!).
For a free version, I would recommend Limiter No. 6 by Vladg/sound. Just use either the limiter or the clipper. Experiment with both and see which you prefer. I usually use a clipper with a 4 or 6dB knee. There are many others out there that might be simpler if Limiter No. 6 seems overly complicated and your DAW probably has a built-in one that might be okay (or it might suck).
P.S. - I would not follow the advice of the previous posters. Nothing against them, I just don't think it's appropriate advice for the problem you are having.