I thought beetles didn't care about the RH, just the temperature? In which case your igloo may be running a bit on the warm side and you may want to relocate it--I could very well be wrong here, though.

I would ask a friend if they have a freezer that you could use for a couple days to freeze the sticks just to make sure... But I'm paranoid about things like this and wouldn't want to take the chance of losing anymore sticks to the little buggers.

The method you're using now seems like it will work well enough, so long as there's humidifiers in all of the ziplocs, but I would make sure that everything is being stored <70 degrees, and I would have just pitched the whole box that the beetles came out of. Not sure what would want to make you keep a questionable box of cigars that beetles came out of...