How can I programmatically disable the "Preview" button in a content type?
For programming disabling use special variable:  

variable_set('node_preview_' . $content_type, '0');


For default node options "Published" (status), "Promoted" (promote), "Sticky" (sticky) and "New revision" (revision) use variable "node_options_" . $content_type, which takes array as a value.
Example can be found in standard installation profile:  

// Default "Basic page" to not be promoted and have comments disabled.
variable_set('node_options_page', array('status'));