I can't use models that were made or edited using 2.80 in 2.79 without the UI acting weird.
2.8 was a compatibly braking release, meaning files edited in 2.8x will not work in older versions, even 2.79b.
That interface acting weird is normal and expected when opening a 2.8x file in 2.7x (or any pre 2.8 version). I've had blender flat out crash when trying to open a 2.8 file.
Fear not, you are not locked to 2.8.
Create a new file in blender 2.7x and append whatever you need from the 2.8 file. I have had appending the whole scene fail, but appending objects always worked for me. Simply
From the Info window File > Append or ShiftF1 then find the 2.8 file. Go to the objects category, and if needed simply select everything.
Proof this really works
I just tested this with this Tesla Model S made for eevee. It is setup for eevee so obviously it's 2.8, even the description says "Blender 2.80 required"
Yet I simply selected all the objects when appending and as you can see it works perfectly (even the materials!)
Export the object in .fbx format. Only catch is that you have to apply all modifyers. Upgrading to 2.8 is worth it, don't believe the talk about it being difficult to transition to. It's very easy.