moderate to severe acne, is due to 100% genetics, and has very little to nothing to do with what you eat, drink, what you do, etc
Yes, genetics is the foundation for acne and, yes, there is no cure for acne. But there are ways to successfully treat acne -- whether it is via topicals, drugs or lifestyle changes. Just because you have a genetic predisposition for acne does not mean that you are doomed to suffer the effects of acne for the rest, or most, of your life. Not to mention the influence of epigenetics which can alter gene expression. Lifestyle and environmental changes will certainly not have any influence on the genome but it can affect the epigenome and/or it can affect the many pathways that lead to acne.
To the OP: I am a little concerned that his weight lifting regimen might be partly (I would venture to say mostly) responsible for triggering his acne. Weight lifting does alter hormones and in a time where he is already going through a lot of hormonal changes, it can just add more fuel to the fire. I am NOT suggesting that he should stop weight lifting; weight lifting has a plethora of positive effects. I am just saying the hormonal changes from weight lifting may be the likely culprit behind his acne. There are supplements that many weight lifters use to combat the negative effects of weight lifting / excess androgens, but considering his age, I would stay away from them for now. It's great that you stopped the dairy! I am not sure if the probiotics would be really effective right now. I would suggest natural probiotics instead, directly from food (kimchee, sauerkraut, other fermented foods). Hopefully, the Stieva A works! I really don't think his acne looks that bad.