It would help, but if you need TRT you need TRT. 

It's all about eating more, see www.massdiet.com

As for the back pain, see a specialist but also peep this:

I need a long list! LOL

L-Glutamine and L-Arginine.

I believe prep can be very detrimental to health and cause some severe mental challenges. You have to be obsessive to be great, but when it starts taking over your life, it is an issue. See this:

Yes, this will set you back and sabotage your success

I am not an advocate of "cheat meals" but the increase in thyroid output (short lived) and the psychological break from dieting are two

If on TRT, you will be fine regardless of diet

Fiber supplements help, but just eat more broccoli!

I think intermittent fasting is silly and not necessary. But you NEED to be in a deficit.

See www.dropfactorbook.com

If 18, SURE! I recommend anything I would recommend for older people. My list:

--Creatine Monohydrate (take 5g, every day, before training on days you lift) and Beta Alanine at 3g (or buy a preworkout with both like MTS Nutrition CLASH --BCAA (Branched Chain Amino Acids) 14g DURING TRAINING or 2 scoops Machine Fuel --Fish Oil, enough caps to get 3-4g epa/dha daily (any time of day with food): I recommend EthiTech Nutrition --Vitamin D3, 5,000 IU (any time of day with food)

--MTS Nutrition Drop Factor

--MTS Nutrition Whey to meet protein needs

--MTS Nutrition Macrolution for a COMPLETE, EASY MEAL

--MTS Nutrition Machine Greens + Multi --MTS Nutrition Machine UPTAKE Probiotic/Digestive Enzyme

--MTS Nutrition Machine Motion

--MTS Nutrition Vasky

--MTS Nutrition TYRANT

--MTS Nutrition Barracuda PLUS Insurgent

--Ambrosia Overtraining Solution and Nektar

--Ambrosia RITUAL AM