How can I get my work to understand it's not time for me to take FMLA yet and I need to work from home at this point?

All you can do is explain the situation. That your DH is dying. That its been a Godsend that you have been able to work from home because you cannot afford the cost of aides to be there for him while u work outside the house. That things will get bad and Hospice is not there everyday, all day. Thats when you will need full FMLA.

That is pretty much all you can do. There are no laws that say an employer has to accommodate an employee. Please update on how it works out for you.

If your employer is having all other employees, at least ones that do the type of work you do work from in the office then that is what your employer would expect you to do. And I am sure other employees would love to continue to work from home as well.
Can you hire caregivers to come in and do what needs to be done while you are at work?
IF you are the one to hire and you do NOT go through an agency you can instruct someone to give medication to your husband. Given the fact that you have VERY strong medications I would be very careful about who you hire. If your husband can physically pick yo a small cup with pills in it and take it it is possible that a caregiver from an agency could do that. But they can not hand the medication to someone.
I found 2 very good caregivers through the local community college. They had just completed their CNA course and were waiting for the Nursing School Schedule to start. Both were very competent, and kind, and they liked working with 1 person rather than in a facility where they would have had many more.
If your husband is a Veteran the VA may provide a Home Health Aid that can do some things. Again not sure if they can actually give a medication or just instruct your husband to take it.
Your option with your employer would be to take vacation time if you have any as well as use your sick time. Would you be able to work 1/2 day in the office and take vacation or sick the other half? Would they let you work from home half day and in the office the other half.
Work with HR and see what option they might have.
Also you can ask if "time donation" from other employees is an option. If you get quite a few people to "donate" a vacation day to you that might help when taking time off.
One other suggestion. If you are a member of a local church or other religious group ask if there are any retired nurses or others that would like to come sit with your husband while you are at work. If there are several it might mean 1 day a week that someone would have to be there.

If you work for a small business I suggest (as a small business employer) that you help them solve the challenge by proposing different options that would allow you to be at home yet still be able to do 100% of your work. Have you tried asking other co-workers to step in the help you get some coverage in a way that doesn't cost your employer or prevent them from completing their responsibilities? Most people are happy to support others in need for a limited amount of time. I wish you all the best from your work environment and peace in your heart as you support your husband.

I am so sorry for your situation. Have you spoken to his doctor or a social worker to see if there is anything to accommodate your needs? What about help from Council on Aging? Perhaps nursing students could help. Students are always looking for work.