May sound a little strange but is there an interest your husband absolutely loves or once loved? The reason I ask this is because I'm a firm believer in the ability to actively love someone back to life. For example, if your husband's passion was once carpentry, buying an antique carpentry plane is an active way of saying 'I love you thoughtfully. I know who you truly are and I will help you remember who you are, with every consideration. That plane will be here when you're ready to use it'. Helping imagine a project may entail buying paper and pencils too.
I imagine seeing a counselor is not who he is. He can't identify with this. If he identifies with your expression of love through something like the plane scenario, you may find you develop the ability to gradually raise him to new considerations, such as counseling.
Raising someone out of depression can be an incredibly slow process because often it's the little things that make a difference. A little thing might look something like this:
Ask the kids to make their dad smile at least 5 times a day. So, if you have 3 kids, of course that's 15 smiles plus your 5 times. A total of 20 times. Tell your husband at some stage this plan is in play. Although he may be down during this time, he will know everyone is actively raising him because that's how much he's loved. It may not be enough to simply say 'I love you'. He may feel he doesn't deserve it but insist this is his value, even if he can't see it. Suggest he will come to recognise it if he keeps looking to his family for guidance.
By the way, you may already know alcohol is known to slow metabolism, which doesn't help matters. It's hard to feel energetic when your energy is being sabotaged in such a way. If you can find little ways of tweaking his energy levels you become a very effective detective in the process. One that's a little unusual could involve you or him buying a lego model kit (challenging for adults). With each stage of the model achieved, it has the potential to give a hit of dopamine to the brain.
A weekly massage down at the local physio or shopping centre may help. It can be your gift to him as therapy he can perhaps better relate to at this stage. Giving this treat is another way of saying 'This is how much I care. I care about what feels good for you'.
I wish you the best. I imagine this to be an incredibly heartbreaking frustrating time for you. My thoughts are with you. Treat yourself to that massage too.