Ok. I put the extreme ones down to 4K. I actually brought the 4000 ones UP to 4K, because the engine is optimized for powers of two.
Everything below that ( > 2K ) I took down to 2K.
With normal maps, if they have no information in them, they can be tiny. No point in an empty 4K normal 
I converted them all to 128x128
May I recommend
So you don’t have to do everything from scratch.
Obviously things like the letters and maps need to be high res, but no bigger than a high def screen.
I’m now getting about 30fps, but it’s still whining about wanting another 1G. But it does work 