iPhone 6 - Wifi vs Data

Oh dear... I have three days left until our data plan starts over and I'm at risk of going over due to spotty and slow wifi connections. I have an iPhone 6 that is running iOS 8.4. I bought it at the beginning of June and did not have wifi issues until the beginning of July. Now, I've read online about iOS 8 having lots of wifi issues and the wifried debacle and all the tips, tricks, and work arounds that others have suggested. Short of factory resetting and launching off a backup, I've done everything they've suggested. But something I've noticed is, it's not ALL wifi networks... primarily my home network. It shows as being connected, but when it comes to actually performing... there's no wifi.

However, I have two iPad minis (one running iOS 8.3 and the other running 8.1) and a MacBook Pro running on the same wifi network without problems. We stream Netflix or Hulu through the Xbox without issue. This tells me it's not MediaCom's problem or our router. Great... figured it must be the phone then, or iOS 8.4 at the very least. Further exploration led me to connect to other wifi networks: Starbucks, boyfriend's house, friend's house... wifi works fine. Not as fast as LTE, but it works without cutting out like it does at home. So is it an internet, router, phone, or iOS issue?

Also, on a related note... even connected to wifi at home (or at least it shows as being connected), I can't send long texts or photo messages, but if connected to data, I can.