Well, papilio's response is pretty comprehensive for the gritty details of the sublevels (I may need to bookmark that post).
On top of those specifics, here are a few general points from my own experience, to hopefully complement the above.
Your build seems really Shotgun focused, and running into similar issues as my own. I used to run Unlimited Shotgun Works (jug + brace of shotguns) all the time, and I found it far easier to set up in UV than HMP due to the greater number of sergeants early on. However, I also found that it was a lot harder to use past DL 3 or 4, when fighting the bigger UV mobs, especially Demons. I'd run out of loaded shotguns before they were gone, as the Demons' armour works well against Shrapnel damage (as they take 4 less damage from each blast), and their increased numbers from HMP to UV meant that a group would now survive a dozen or so shotgun blasts to the face, and be ready to chew off mine.
Your late-game weapon set nicely accounts for this, but everything earlier seems to rely on either shotgunnery (probably knockback?) or getting berserk status in melee to survive. I really want to see how you play, since all I can do is make a lot of guesses, and I have no how you approach rooms, handle monster groups, or generally move around while fighting, which would make a big difference given how close-range focused you are.