This question does not have any specific Neurosurgery Point. Hence I am answering this as a physician and not as a Brain Surgeon.
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In most other terminal illness, the patient understands the disease and the consequences. Brain Tumor, especially when it affects the speech and thought process, interferes with the individual's understanding of his illness and hence the burden on the immediate relatives are high.

I understand the difficult situation you are in. You are already over burdened.

(1)
Please don't take the role of a counselor at this moment and increase the (emotional) weight on your shoulders. If he talks about being anxious, listen quietly. Don’t try to change the subject or silence him . When he is finished sharing concerns, encourage him or her by asking, “What do you want to achieve now?”

Then gently say that even you would like to have him in his home, but his condition is that doctors are not ready to discharge him.

You may have to act as per the treating doctor's advice. No doubt about it. But when talking to your husband, please take his side. Say that you want him to be cured and come home and return to normalcy at the earliest (Given the choice, I am sure this is what you will want - So you are not telling a lie. Say this with full conviction). That it is not possible is not the issue. That you want this is the point to be stressed. Read this para again and again and get convinced yourself first.

(2)
Try to get the help of his friends. Try if any of his friends can come to hospital and tell him that he needs to be there

(3)
If he is religious, consider bringing your priest / chaplain and ask them to talk with him