Help me fix my bathtub please

I have multiple sclerosis, and our bathtub/shower is dangerous. We only have one! I've been trying to get help through local agencies for two years. Homeowners insurance won't cover this. I applied with CAC but they say they don't so any structual repairs. PRC has denied me 3 times. The MS Society can only help for hand rails and safety features, not for repairs. It's been getting worse and worse, and now it's terrifying. I keep trying to save money, but something always comes up. It's just getting desperate. I need to get this fixed as soon as possible because contractors don't want to do this kind of work in winter.
There's a huge hole in the floor of the tub, and a 1" gap all around the tub itself. The sub flooring needs replaced all around it, including under the water heater. Bugs keep finding their way in, and we even had a mole come in through the hole! Its become a big safety hazard for all of us. I have a hard time healing from wounds, so I need to be able to have a way to bathe safely. I'm especially prone to infections, because of my compromised immune system. We can't use the bathtub at all, and showers are terrifying. Please consider helping me and my family.