I think this is a really balanced, thoughtful post with a lot of good advice. We struggled to conceive, although I didn't experience losses - which I'm so sorry you have had to go through.
Struggling with fertility is a massive strain on couples. Undoubtedly a huge amount of the physical and emotional stress falls to women, but men find it very difficult too. I think the odd beer or glass of wine can as PP says, "take the edge off" for them. Let them pretend it's not happening, and shirk the responsibility of it all. Numb the big emotions. It's a human but ultimately poor coping mechanism.
Fertility struggles are a relentless cycle of opportunity and loss and inherently focus on what (and impliedly, who) is to "blame". It's not a helpful narrative, it often remains a mystery, and either way is a minefield for relationships. To get by emotionally and stay close, I think it requires a really shared goal, a lot of very honest conversations, true compassion towards each other and - as other PPs have said - loving actions, rather than words.
To me, that would mean showing curiosity around his experience. Ask the hard questions - why can't he get through a week without a beer? Is it to escape what's going on? To feel normal? Does he resent that you are both having to go through this experience, and this is how he's rebelling against it? How else could he meet those emotional needs, more constructively? He needs to reckon with these issues, and in a committed relationship, you are his safe person to explore that with.
And while I think you should extend him that grace, he equally owes you the same compassion and support. At the end of the day, he should absolutely be able to get on board and give up alcohol. He should recognise that with what you are putting your body and your heart through towards your shared goal of bearing his child, it is the least he can do. So while I, unlike others, would take a gentler approach to exploring his problem - I do also think that ultimately he needs to get his act together.
I really hope he does OP. Wishing you luck💐