My 4a went from 3 day battery life to less than a day, immediately after the "update".
Data is cheap where I live, but also I dont use my phone to stream music/video.
Sounds like you should move your AP? There's no way that communicating with an AP tens of feet away is going to require less power than communicating with a tower hundreds of feet away.
>I also find that on wifi data, apps constantly update and sync themselves - they don't do this on metered network data.
You can set wifi connections to "metered" on both android and ios. It doesn't allow you to cut off data entirely (like you can on cellular data), but should have similar effects to being on cellular.