As soon as I read your post, I knew that the great majority of the replies in this thread were going to be telling you to focus on cleaning your diet up, and that is correct in that doing so will help you get better results and also help supplements work better for you.
However, since everyone else covered that part pretty well haha, I wanted to address your last question about "is there anything that can slow down the breakdown of muscle tissue from such chaotic eating and/or help with the muscle fullness".
In your situation, my supplement of choice would Phosphatidic Acid XT because it contains Mediator Phosphatidic Acid, Apigenin, and Senactiv. Apigenin has a lot of overall health benefits as well as some potential muscle building and sparing benefits and Senactiv is great for workout performance and has some other great benefits, but the all-star ingredient is Mediator Phosphatidic Acid.
Here's an excerpt from the product write up that explains Mediator PA very well imo:
What is Mediator® Phosphatidic Acid?
Mediator® Phosphatidic Acid (PA) is a natural muscle building supplement that has been shown to directly activate mTOR – the signaling pathway that drives muscle protein synthesis in humans. Research involving resistance trained athletes has found that supplementing with Mediator® PA leads to increases in lean muscle gains, strength gains, fat loss, and improved body-composition.
Mediator® Phosphatidic Acid offers what many other overhyped supposed muscle building supplements lack – research in humans showing real gains in muscle size and strength!
Real World Results:
Increased Strength & Size:
Research has shown that lifters taking 1,500 mg. per day of Mediator® PA (750 mg. actual Phosphatidic Acid) increased their squat strength by 12.7% and their lean body mass by 2.6%. A study at the University of Tampa on 28 resistance-trained subjects who trained hard 3 times per week actually doubled the amount of muscle they gained as compared to subjects that followed the same training protocol but were only taking a placebo.
Fat Loss & Improved Body Recomposition:
Research has shown that individuals supplementing with phosphatidic acid in conjunction with resistance training lost 2.8 lbs. of body fat compared to only 1.1 lbs. in the placebo control group.
Recovery:
Muscle growth and recovery is largely governed by a balance of protein synthesis vs. protein breakdown, also commonly referred to as anabolism vs. catabolism or the body being in an anabolic state vs. a catabolic state.
Phosphatidic Acid has both anabolic and anti-catabolic properties!
In addition to stimulating increased protein synthesis, Phosphatidic Acid also helps limit catabolism by reducing the expression of certain genes that encourage muscle protein breakdown.
Think of this as if your diet and training is correct, your body is perpetually in a state of trying to build muscle and break down muscle at the same time. So whichever side wins – anabolism vs. catabolism or anabolic vs. catabolic states – largely determines your net muscle yields or losses.
Phosphatidic Acid helps tip the scales in your favor by stimulating increased protein synthesis (anabolism/anabolic state) and also helping decrease catabolism/the catabolic state – so it packs a potent one-two punch towards helping you achieve your muscle building potential and goals.
^^^^ I think you can see from that how it would help you.
And then, the more you clean your diet up over time, the more it can help you.
Here is a link to the Phosphatidic Acid XT intro thread to see some other people's results:
Natural Anabolic Muscle Builder Ultra-Potent mTOR Activator 1,500 Mg. Mediator® Per Serving Look Better. Feel Better. Perform Better. 1,500 Mg. Mediator® 50 Mg. Apigenin (as ApiPure™) 50 Mg. Senactiv® 50 Mg. AstraGin® 5 Mg. Bioperine® Mediator® Phosphatidic Acid (PA) has been shown to...
anabolicminds.com
Here is a link to the full product write up and info that goes into more detail about Mediator PA and the other ingredients:
Natural Anabolic Muscle Builder. 1,500 Mg. Mediator Phosphatidic Acid Per Serving. Lean Muscle, Strength, Size, Recovery, & More. Plus Senactiv, ApiPure Apigenin, AstraGin, & Bioperine.
seriousnutritionsolutions.com
^^^ If you decide to try it soon, make sure to use coupon code blackfriday30 to save 30% off on it.