In no particular order I see you option as.
- Contest the will to get the money. This will cost everybody a lot and probably wont end well.
- Convince the executor to make as ( @Sarah J suggested) to pass the trust to the Public trustee. Just remember they are a bureaucracy and will do their duty but don’t "care" about you. But you wont have the family history to deal with.
- Leave thing as they are.