How screwed am I?

Looks like powdery mildew to me. I used a product called Banish, it’s a natural terpene called geraniol that works pretty well. It’s very expensive tho. I’ve had at least the same or better results with hydrogen peroxide. You’re well into flower though and close to harvest. It will be interesting to hear what others have to say. I’ve heard of people harvesting and washing the flowers in hydrogen peroxide. Powdery mildew is not as bad as bud rot but also not something you want to smoke. Figure out how this happened. Did your humidity get too high? Do you have enough ventilation? Do you mist your plants? It’s important to correct the issue so you don’t have the same issue in your next plants. Also important to consider the tent will need to be thoroughly cleaned as surely there are spores in there. They make products to disinfect the tent. Sorry this happened to you. Good luck!!