A little puzzled on this post/pic?
Are you suggesting you will be disregarding the advice and using the GoPro Wifi App for FPV with that rig?
You are right, DJI say not to use Wifi. This is because it transmits on 2.4ghz... as does the Phantom Transmitter/Reciever. If the Wifi signal from the GoPro is a more powerful signal than that from the TX it 'can' (not will) cause the Phantom to think the GoPro is the TX. If you are lucky it'll glitch. If you are unlucky those signals might translate as 'trottle forward'.... by by birdie, camera and money. Of course if you are getting a Hero3 (not a Hero3+) then Wifi has a 30 second(ish) latency delay so it'd be unusable anyway.
You say it 'only happens when you fly too far from the TX?' but how far is too far? It is an unknown factor and while I sound like a grandad for saying this it is kind of negligent for trying it.
Of course no one can stop you from doing this but why risk all that money and equiptment (and the potential for a Phantom landing on someone) when even the manufacturer advises against it? (DJI currently stand by their own faulty firmware so when they say something can go wrong... its a red flag event!). I'm not against experimenting here and there but if you chose to do so make sure you are in the middle of nowhere to reduce risk. I am sure you are a sensible chap and will have considered that already.
Get yourself an FPV setup like a Fat Shark Predator V2, Dominator or Attitude (the latter are better quality but pricey). All are safe, reliable, have no latency and a 1-2km range with good Cloverleaf antenna setup (I get 1.3km with poorly soldered DIY made antenna).
If you want a monitor solution rather than goggles the Fatshark is still an option as you can plug the screen into the goggles and get best of both worlds.
Where to buy depends on your location so please post this so we can advise (better still add it to your profile).
Hope that didn't come across to grandfather like! If I got the wrong end of the stick please feel free to tell me to shut up

I just hate seeing people posting a "so i lost my Phantom today". Even the idea of losing mine terrifys me!
Happy flying.