Wow . . . a lot of emotional decisions to make, on which I am no expert.
On the business side though, my suggestion is to run the existing company, turn it into something great and then sell it and fund your new idea. Remember: The biggest challenge with running a family business is the question of whether senior family members let you run it as your own.
If not, then go do your own thing.
From a pure financial viewpoint, you will generally make a lot more money a lot faster over-hauling an existing average business than you will starting something from scratch.
All the Best