Well, I can tell you I've definitely seen much worse coops than this! Other than your wire and window problems, it looks like everything is nice and solid, and you have enough space for quite a flock!

My first tip for your cleanup is to get a better mask, if you're using a standard cloth N95. The cloth masks are better than nothing, but the respirator masks that painters use with the replaceable filter cartridges aren't very expensive, and they work so much better that even the smell won't be as bad.

As far as cleaning goes, I recommend first raking up what you can, then blowing it out if you have a blower, then spraying it with a hose. A pressure washer shouldn't really be necessary, but if you have one, they always do a better job and usually use less water.

Once you've cleaned it, just letting it dry out and letting in some sunlight for a few days should sterilize it well enough. If you prefer to use a cleaner, anything disinfectant soap should do the job, just make sure all the 'cleaner' smell is gone before you move your chickens in. For a quick and easy sterilization, Lysol spray disinfectant is amazing. I'm not personally a fan of disinfectants, unless there is a known reason to use them, because you're usually killing a lot more beneficial bacteria than you are eliminating harmful ones.

Also, a note about the fencing on your chicken enclosure: that fence will not keep out most predators in the weasel family. They won't usually attack chickens outside during daylight, but something to keep in mind if you have a lot of weasels, mink, fishers, or martins in your area. Fox will also dig under it, if they have an opportunity.

The old dog area with the nesting box access may be a good place to set up an area for brooding, if you plan on raising your own. Separate brooding space is not always necessary, especially with small flocks, but if you plan on having over 30 chickens you're likely to need it. You may also want to keep some separate enclosure space, if you plan on eventually culling roosters for meat.

Best of luck with your chickens, and with the rest of your self-sufficiency journey! Feel free to ask any questions you have. I don't have all the answers, but I've been around chickens and chicken farms my whole life.

P.S.- A link to the kind of mask I was talking about:
https://www.amazon.com/Respirator-Reusable-Polishing-Woodworking-Protection/dp/B08Z9YGNMZ/