OP, you are playing with fire. You are humiliating your H and making a public mockery of him with your flirtatious emotional affair and your kissing in the pub. You and WorkMan have made him an object of pity and gossip. That is so wrong.
H has an illness which is being treated with therapy and medication. If the antidepressants aren’t helping, his dosage needs to be reevaluated. That being said, he needs to cut out the alcohol, as it is a depressant. Also, mixing alcohol with some antidepressants results in sedation.
When you say he drinks ‘quite a bit,’ how much do you mean? Besides the probability of alcohol exacerbating his depression, of great concern is his ability to properly care for the children if he is drinking, sedated or hungover.
OP, while your family is in a crisis, you are perpetrating a destructive betrayal of your H and children. When you pursue illicit validation from this WorkMan, you are actually sabotaging your well-being and harming your family.
You need to shut down the infidelity, focus on your marriage, and make your decisions with clarity and integrity. H’s meds possibly need tweaking and it is up to him to find out. His alcohol consumption needs to be addressed. You cannot control that, but if it’s a problem, consider attending Al-Anon for support. You should not stay with an active alcoholic.
In my view, you would greatly benefit from individual counseling. You need that support.