Although I have never used the MES, I have heard several positive things about it, and I know many many members here use it. Granted, it doesn't have some of the features of the cardboard box but. LOL. I'm sorry, I had to throw that one out there. Don't be mad
I was just trying to figure out why you think you couldn't distinguish the lean meat from the fat. Did you have the meat chilled prior to grinding? Almost to the point of freezing? Cutting meat that is soft will not grind so much as it will smear and tear it when it goes thru the cutting blade and plate.
Do you have a dedicated stuffer or did you use the grinder to stuff? If so, did you grind right into the casings or did you grind, then load the grinder back up and run everything back thru.
I was just looking at your last pics. If you can't get your temps up to where you want them, I think you could still get a decent smoke with that box setup, but you would still have to finish them off in the oven to achieve final internal temp. If you do this again, that flap on the bottom, leave that open, and crack the top more than what you have. Remember, it only take a little smoke to make a nice flavor. I'm saying this because you commented on the final product having a somewhat bitter taste, most likely caused by stale smoke.
Check out that MES, I don't think you could go wrong with that, in fact, I am strongly considering getting one for when I do smaller smokes.