Carol,

Could you ask your uncle directly, via email, the questions you have and the needs you feel you will have some day that you might need help with? Maybe you already have been very specific, I don't know.
It sounds to me that your uncle might not know what to say right now.
If he knows specifically what ways you would like him to help, then he could respond and say what he is able and willing to do, when the need is there.

Are there other ways you could prepare for being alone, something we all have to prepare for and adjust to. That might be a different living arrangement, or more reliance on community programs and help.

It sounds very disappointing and stressful for you right now. I don't think your uncle meant to let you down, but it does sound like he's being evasive for what could be many reasons. Perhaps it would be best to clear the air by phone or email?