There are no certainties in law.
Your uncle appears to know he has done the wrong thing and wants to frighten you off. Based on your information you have a very good chance.
Without hearing from your uncle I can't evaluate how strong his case is going to be. My guess is that he'll say your grandmother verbally approved all the expenditure/gifts.
Having your grandmother declared as having legal capacity will help, especially if she contradicts the uncle's assertions.
Your uncle appears to know he has done the wrong thing and wants to frighten you off. Based on your information you have a very good chance.
Without hearing from your uncle I can't evaluate how strong his case is going to be. My guess is that he'll say your grandmother verbally approved all the expenditure/gifts.
Having your grandmother declared as having legal capacity will help, especially if she contradicts the uncle's assertions.