I need phone advice. Note 4 is Junk

Hello Everyone.
I'll TRY to keep this short and sweet.
I'm having an almost tear inducing time trying to find a phone for me.

I went form a Nokia E63 to a Nokia E72. Loved these both.
Went to a Blackberry Q10, which was amazing. but was too small.
Upgraded to a Blackberry Passport, which is beyond perfect; but is starting to show webpage incompatibility.

I've accepted that until the new Nokia launch (come on Q4 2016!) or Q1 2017, when the new Blackberry qwerty android comes out, I need something to bide my time.

I bought a second hand (proven not stolen, receipt and such) Samsung Galaxy Note 4. I owned a Note1 and thought I knew what I was in for…. nope.

The Note1 was GREAT.
CyanogenMod had bothered to do a full release for it, which I flashed Day1 and loved the everloving sh!t out of it!

The note 4?
No stable ROM options.
I'm on the Marshmallow ROM sent OTA by Telstra, and have done a factory reset.
TouchWiz is impossible to use, options are disabled, or missing entirely (hold back to force close, for example)
You can't flash a custom ROM without triggering a KNOX warranty Bit flip (so people know its been rooted)
The GPS is close, but seems to randomly 'jump' from one side of the street to another while I'm perfectly still.
The WiFi is the killer here. It disconnects after 5 seconds of inactivity, and doesnt try to reconect, despite being in range.

So, with the official ROM, and no easy way to flash custom ROMS, and it being shit, I'm in need of help.
I was planning to move phone 'full time' till a modern android phone comes out I like.

Prior to this, I borrowed a ZTE Blade D, and it ran Pokemon GO just fine, using Wifi hotspotting from my Blackberry.
But I'd like to actually switch full time, so I'm used to android for the new BB's and Nokias to come.

I've considered an Oppo F1 (now that they're $199 at Optus prepaid), but the battery life is concerning me. I'm used to my Passport being able to stretch into the 3rd day for battery, but some people report less than 24 hours with the F1.

I keep reading Band 28 (700mhz) LTE is important, and all my previous phones have had it;
but does it simply mean my phone will drop back to 3G instead of 4G? HSDPA? 7.2mbps is faster than my phone internet connection, so that's fine.

TO cut the story short;
I need a phone thats:
-Below $300
-Can Have Cyanogen installed (or comes with ASOP and can be rooted)
-Will run Pokemon GO (AR is not needed, so dont stress about Gyro)
-3GB of RAM is preferred, but I'm open to discussion on why 2GB is enough.
-5.5" screen or bigger. I MIGHT consider 5" if its super cheap, but I have vision problems, and also like the larger keyboard.
-BATTERY LIFE!