Does chantix release histamine?

Not that I know of. it acts on nicotine subreceptors (alpha2beta4 as I remember), and does not release histamine. I see you have a mast cell disorder, so you should be running this by the allerist/immunologist or rheumatologist you are seeing for that condition.
Definitely, no. Chantix is an alpha4beta2 nicotinic receptor partial agonist and also is an antagonist at histamine H1 receptors.