After drop, battery life extremly short and wifi grey out iPhone 6

Hello Nick! i can help you with the wifi, what is most likely happened is that the wifi anetenna had a big shock of the fall, and might been "jumped" out of it socket, but i have only experiensed this at Iphone 4/4s.

for the wifi antenna see HERE & HERE

i would've changed both the antenna it self, and the cable just to be on the safe side, aswell these are quite cheap products :)

but maybe for the battery you could buy a new one to help it HERE

Im sorry if i was to no help, but good luck buddy! :) Happy fixing ;)

I had the same problem, if the Bluetooth wheel is spinning as well and in settings under wifi address it says NA you'll need to replace you wifi chip, YouTube how to replace iPhone 6 wifi chip and that tell you how to do it, however it requires soldering skills and a lot of effort, best bet if you inexperienced is to take it to a repair shop tell them the problem and get it done there

Hope I helped

Regards

Lucas