Go to the Bamboo Society website and carefully choose your variety. Bamboo is terribly invasive can take over your whole property and spread to your neighbors. Once established it's nearly impossible to eradicate.
I would avoid the permethrin. There's little benefit vs the continued exposure to the pesticide. Give your birds a good dust bathing space and add some diatomaceous earth. You won't have a mite problem.
You could sink some piers into the ground to bolt the coop to. Just sitting an elevated coop on cement blocks is not a good idea because the structure is not heavy (as buildings go) and a strong wind could blow it off the blocks. If you put in piers and leveled them across the top you could...
I would think that the raccoons would be stronger and smarter than a coyote so if you stop the coon the coyote won't be a problem. I'd be interested in other opinions.