Perhaps we need to realise that both alcoholism, and MLC are a response to a deep disturbance, and a sign that all is not well.
it does seem that many MLCers go through a period at least of heavy drinking, but in my case my xh is not and never has been an alcoholic. Whatever it is, they are running and trying to hide from their demons. Distractions include OW, and generally stupid behaviour.
I think we have to set boundaries, and all the information I have read about dealing with drug and alcohol abuse [I worked as a volunteer for a time with this group] indicates that you must set boundaries and stick to them. This is not the same as nagging.
Same with MLC. Our boundaries can be different. Mine are very tough. Not suggesting they are right for everyone, but they are right for me.
Your h may be sick, but ultimately we all have to take responsibility for who we are, and our decisions. Your h could face up to his drinking issues and do something or he can continue to run and hide. As long as he is an alcoholic your relationship will be co-dependency at best. Until he sorts himself out and stops drinking he cannot have meaningful relationship with anyone.
You are not the problem, so do not beat yourself up. This is about him.