Does anyone know if there is a quicker way to get adept builders up to master builders than fixing the huts because mine have been doing so for 3 days now and they still are only adept?!?

Have you got any other puzzles left to solve that will take building? If so, I wouldn't worry too much about them fixing the huts. Even one more puzzle to be constructed will give you a master in no time, as long as you don't put a heap of people on the task.
If you've completed every building task, then make only one person a builder, and let him/her do all the fixing.

I have the treasure chest puzzle left and I need a master builder for it but all the building puzzles I have done so what should I do?

Choose the most adept builder, and one not too near elderly, and make that person the sole builder. He will more likely stick to fixing huts more consistently... and then ... patience

And you could always start another game in one of the other slots in the meantime.