I know how you feel. I would've liked to see more of what happened to the characters, but I think the film gave us enough to draw our own conclusions. Bart went to the uncle's house to confront him, maybe physically, but once he saw how pathetic the uncle looked, I think Bart just gave him a severe warning not to contact Mackenzie anymore, or he'd go to the police. I hope Bart and Mackenzie go to the police anyway.

Mackenzie looks at peace when she finds the note from Bart on the map. She knows that she's not left to fend for herself once again; she can find Bart in Seattle later and he will most likely help her look for her mom. I have the most questions about the mom. How could she go AWOL from treatment and leave her daughter with no means to contact her? I can't see a mom doing that unless she was really messed up, either with mental illness issues or a drug problem. The film leaves it unclear exactly what the mother's problem is.