Hey Lince,
Your usage of Neem is good, in early flowering and in veg anyway. Neem will kill pistils, some say only if it's concentrated too much in water, but I have seen it kill pistils when it's very weak concentration. So I neem up until week 3 of flowering, when pistils really start coming out. After that you need to use something that won't harm your pistils/buds. Greencure is something a fellow grower of mine started using and he says it works great. I've tried Serenade and it turns your buds yellow, so you don't wanna use that.
After much experimentation I found the most effective cure for the powdery mildew was something quite simple: Hydrogen Peroxide/water. One part Hydrogen peroxide to 5 parts water. This will kill the PM on contact with the water peroxide spray. And it doesn't harm your buds at all. You can spray this the day you harvest if you want.
Spray the hell out of your plants with this and you should be fine. Also regarding foliar spray during flowering: there are lots of foliar spray applications that you can do during flowering that won't harm your buds, affect their taste, and will actually give you better results.