There is no perfect formula and with the amount of PED I use - not much - I am sure it helps but I still get injured if I train too frequently. You have to experiment. I have been doing 1 body part a day as a change - never tried it before and much to my surprise I still can't train more than two days in a row. I listen to my body as I know the repercussions if I don't. A slight pull which can turn into a chronic pain and issue you have to rehab and hinders progress. A wise man once said this a turtle sport - small progressive gains.
Can't stress this enough - I would rather kill it in the gym today - stretch tomorrow/warm up and I will know immediately good pain from bad pain and even though I want to hit the weights I won't. It isn't out of the ordinary for me to take two days off and then train two days but when I'm in the gym or training at home - I make sure I am making the most out of the time.
You mentioned shakes and weight gainers/ensure. Just my opinion and yes I always have a bottle of whey protein or Vega Sport protein but don't use it everyday - try to get your calories and goal on macros on with real food. Steak, Chicken, Fish, different meats for protein, lots of sources of carbs - vegetables, fruit, rice, potatoes, yams, cream of rice is a favourite of mine for a pre-workout. Good calories / good carb source and you can almost work out as soon as you are done without feeling full. My point is I would throw the ensure out the window, it is crap and sorry if that sounds harsh. Weight gainers maybe if you are a strong man and can't get 5-10 K calories a day, otherwise do your best to get it from food. Real food - eggs are a great source of protein after training, quick to cook, and I wouldn't worry about the yolk. Anyway - you do what you can. Fats aren't your enemy either - healthy fats that is if your in growth mode: EVOO, real PB, almond butter, etc. I can make a meal out of a tablespoon or two of Almond butter, a small piece of meat (a 6 ounce top sirloin steak I cooked at supper) - maybe a cold piece of left over steak, and when I cook potatoes or sweet potatoes I cook more than enough so I can put them in the fridge. I will eat a cooked cold sweet or normal potato. Add up the calories/macros - close to 700 and 35 g carbs/35 g fats/44 g protein. Keep in mind I'm far from perfect hence cooking in advance and knowing how long food will keep in the fridge and that was not including any veggies. I always eat fruit and vegetables. I have to plan out my meals in advance or I won't eat the right food or enough of it.
If it was me I wouldn't train the larger body parts less and arms more but that is me. The reason I say that is I do train train triceps and biceps but they get a major workout when doing other body parts. Any chest/shoulder day includes a lot of pressing and your triceps will often give out before your shoulders or chest. Same with back - I get an incredible pump in biceps and I am careful to all pulls concentrating on pulling with my elbows to eliminate the bicep work.
As much as seems counterproductive - and I am past the days I can do it but I see some guys doing it here they don't even train biceps and triceps: they concentrate on heavy compound exercises like presses, dead lifts, bent rows, squats (not for arms at all), shoulder presses of different variations and upright rows for a change. Just a suggestion when you hit a wall and need a change if your body can take it.
I wouldn't worry about the PED angle - I am on TRT and periodically throw a small amount of another compound in like Primo or NPP but only 150 mg per week. My gains are from food. I'm not dim and know if your blasting more PED's you can do more but I don't care if you are on 1000 mg of anything - working out 6 days a week if you truly are balls to the wall training you will inevitably end up with an injury. Most people try to work through it and end up with a worse problem. There is nothing wrong with feeling a 'bad' pain and walking out and taking a few weeks off just stretching and getting therapy. I use a rock hard ball and hard foam rollers all the time to work out issues prior to training and if I pull something.
I am all over the pond here with this post but my main point is: there is no perfect formula, food is your friend more so that sugar drinks like ensure to get calories unless you have to for being strongman, PED's aren't your solution as you can't keep it up. It isn't healthy and you need to learn to eat.
@FitTrader, who had been through it all, once said he never knew about growth until he really learned about eating.
For what is worth -
@Funnyman I believe is very reasonable in cost and worth way more than a few bottles of test, I wouldn't hesitate to hire him for a phone consult and get suggestions.
This is not a lecture or saying don't try the things you are trying but consider alternatives. I can't say do this or that for certain, nor can anyone else as we are different phsiologically.
Whatever you do best of luck!