Best of Luck
Good to hear you made the plunge. Solar heating both for personal use and for water is a good start and is something that can be done with simple tools and equipment. Conserve first then build more is a good idea.
How close is the nearby town? I ask because the idea of being out all alone in a “doomstead” isn’t the best way for resilience. Being a member of a small community is always better. Skills and resources that are hard to learn personally are much easier accessed with some sort of community. That you rented on the island, and so should be a member of the community will help.
Best of luck.