Sounds like you are doing a good job, keep it up!
As for feeling like you are being bitten at night in bed, that sounds miserable! Read @rosemarythyme post found HERE where she shares some tips of having the mites in the house/feeling they are in bed. She may want to chime in with more tips.
Hopefully with the suggestions given, you'll be able to get these buggers eliminated.
Ugggh! I agree with you, burn that straw. I can't name the mite things in the straw, but a lot of times mites can be brought in with straw. I wonder if they are what Old Timers call "straw tick mites"...
They are not bringing them in, you just have a heavy infestation in your coop. You will have a battle on your hands for a good while.
What is the plastic looking material in the last photo?