@denise96, I know that you feel helpless or that you aren't doing enough, but you're doing everything. You are loving him and caring for him, that's everything.
I've lived with lung cancer for 4+ years and I've watched people do everything 'right'; exercise, eating healthy, trying all sorts of alternative treatments, with large prayer networks. I can't explain who makes it through this disease and who doesn't. We just don't get to make sense of everything in life. Sometimes we don't have the power to direct and control a situation, or another person. We do have the power to be present in a way that we won't regret later. You are doing so much to help him. I'm not sure when the right time for hospice is but know that helping him through that stage is one of the best gifts that you can give him. It won't be easy, and he may not be able to express it, but having you there will be the ultimate comfort to him.
Hospice workers can be wonderful people. They really are a special gift to all of us. You may want to consult your husband's doctor or a trusted nurse about the timing of when to bring hospice in. They would be best at assessing the situation. In past messages you've mentioned a pastor. Have you spoken to them recently? It may help you to reach out to them too.