I am a 55 yo f living in wa and have barrett's esophagus. would marijuana use 2-4x/year increase chance of esophageal cancer?

No: there is no evidence that marijuana usage increases the risk of esophageal cancer. It would be even less likely, given the infrequent nature of your usage. You should follow your anti-reflux regimen closely though, given that you have Barrett's esophagus. If you're overly concerned about the marijuana smoke, you could consider vaporization or edibles....Good luck.