You are minimising your own feelings now that they have been uncovered.
You have adapted your behaviour (not allowing friends over) because you are ashamed.
No one needs to feel ashamed in their own home.
An alcoholic is one 24/7. They are either moody, quiet/sullen when hungover and plotting their next drink - so they consumed and self focused. Or they are drunk and slurring. Both states are not available for a relationship.
Its your home and your rules for your DC childhood.
Of course they sense the unpleasantness and your anxiety and distress in the house.
Alcoholism is a a progressive disease - I suggest that is why his previous relationships ended and it will continue to progress and his life deteriorates - socially, career wise, health and financially.
Are you going to continue enabling and propping up this deteriorating mess in your home at the expense of your DCs own childhood and future MH and emotional well-being.
You will not find one adult child of an alcoholic or any agency that will agree with you that this is having no impact on your DCs.