This is an incredibly difficult subject with much wisdom shared. I agree with the reality that individuals have to want to change for change to occur, so understanding the root cause/contributing factors will be vital if you want to help. This is a very different proposition from just asking/telling people to change.
Behaviour change is very difficult to make - all of us have habits that we dislike but we continue with them. For some people the results are very visible, such as described here, but others are invisible. Just because you can't see the results for the habits each of us have doesn't make us any better than someone who is overweight or addicted to drugs. Sometimes reflecting on what makes change difficult for us can bring understanding of why it is hard for others.
I wanted to pick up on the alcohol. Some quick maths and basic assumptions (like the strength of the home brew wine) suggests to me that the weekend load you mention (at 1 case of beer) adds up to 8,000 kcal from the alcohol content alone (nevermind all the other energy content). Even split a couple of ways this is a major source of energy. Understanding why he drinks so heavily (it also works out to be 252 units) may be one in road to identifying strategies that could help. Perhaps forgetting the food entirely and seeing if he would seek help from an alcohol service may bear fruits.
Lastly, because change is hard with so many prompts around us undermining attempts to do things differently you need positive motivators to encourage and help you maintain it when things are difficult. Negative motivators are not as strong and changing things out of fear will only get you so far before resentment sets in. So helping him identify what he, as an individual, gains by making change and finding ways to reinforce these gains alongside opportunities to celebrate success along the way are vital.
So as a practical example I ask people who I'm helping give up smoking to identify what they gain as a result. For some people that is financial and I ask them what they intend to do instead with the money. For some that is a holiday they have dreamt of. So getting clippings from the brochures and putting them in a wallet, on the noticeboard, on the sun visor in the car and so on, where they provide a constant positive reminder of how they are gaining/benefitting, can provide that motivational support.