Sometimes life really is unfair. Your husband has had a number of stressors piled up on each other at an age and time when life is supposed to be getting a little easier, not harder. It must be both terrifying and sad to watch this good man crumble like this. I’m sure the psychiatrist is doing the best he can with the medications but it may well be that his psychiatric condition is only part of the picture.
By all means, please, please follow through with the neurologist. There are a number of medical conditions that can provoke agitation, depression, and thought disturbances (like the religiosity). It may well be that the psychotropic drugs aren’t working because the problem isn’t entirely psychiatric.
If he is medically okay, then it really is time to see a psychologist. Pills alone aren’t going to help him feel better about himself or learn how to manage the multiple stresses he is under. His ego has taken a major wallop. For years, he got along fine without being literate and now technology is making him feel inadequate and scared. His role as a provider is being threatened. If, like most men, his self-esteem is deeply tied to his work, that too is under siege. His mother is dying. He doesn’t feel in control of his own mind. He worries about worrying you and letting you and the family down. It’s no wonder to me that he is so upset.
A psychologist or other licensed mental health counselor can help him set priorities and learn new ways to manage stress. He will get emotional support and a positive sounding board for his anger and fears. Because he knows you love him and care for him, your husband probably protects you from some of his thoughts and feelings. He doesn’t need to do that with a therapist.
I understand that money is tight and your husband is therefore reluctant to pay a therapist. Many companies offer free counseling through an Employee Assistance Program as part of their benefit package. You might see if your husband’s workplace has such a program. If not, ask your doctor if there is a clinic or a private practice that offers a sliding fee scale. Consider that paying for some sessions now may help prevent your husband from further deteriorization and pain.
I wish you both well.