I agree with JoeCa1i on the pull the plants suggestion.
My friend, I have done battle with powdery mildew a few times. I've bought damn near every fungicide imaginable and still lost the battle. On a different note, I see a lot of folks on these boards say that smoking the buds with PM will make you sick. I can truly only speak for myself....but I did bring some willies wonder with PM to the end of budding and still smoked it. No lung irritations or illnesses and I'm still alive to type this! Again, that's just me. And I tried my best to cut any severe PM coated buds down to where you couldn't see any PM any longer when trimming. That said, IMHO your best bet is to yank the plants, scrub the walls and everything down with bleach or H2O2 and start again.
Then there's the bugs. Webs + Black bugs = Spider Mites in my experience. This means you are double screwed. Spider Mites are almost impossible to get rid of during budding without spraying the only chemicals that seem to kill them (Avid and Floramite from what I can tell), but you should never spray on buds as they are really reserved for the veg cycle. I've heard Neem Oil works, but is messy and am not sure if it kills the eggs. So you'd have to repeat treatments.
It truly pains me to type this response. I genuinely hope your situation works out. But you should know that as a grower...and again in my opinion.....it's not if you'll ever get spider mites or powdery mildew....but when. The PM can be avoided from the start with a dehumidifier and the spider mites in veg can be sprayed. Also, keep dogs and cats out of your grow room. I'm pretty sure my yellow lab being in my grow room is the reason behind my spider mite infestation. It literally destroyed my entire crop in a matter of days. But that was before I checked every day religiously for them! Spider Mites are practically Bin Laden on my hatred scale!
Hope this helps....good luck!