Could a brain pacemaker be used to treat autism disorders?

No, but creative. Since actual changes in size & density of neurons ( nerve cells), disruptions in connections between nerve cells and number of connections have been found in parts of the brain that process emotions ((e.g., hippocampus) & in the cerebellum, changing the electrical impulses would probably not correct function. Keep thinking, though. Intensive, repetitive behavioral & educational therapy does help.
No. Currently , there are no effective treatment for autism, but for co- morbid condition and related symptoms. They found that older men if they decide to get children can put their children at risk for autistic d/o, .