You could get a Reverb G2 when they are released, they are supposed to have very sharp lenses and cheaper than the Index.
I thought he said he had a 1070? A 1070 can't run a rverb at full resolution on PC2. -Not even when set to potato.
I know the G2 has the half-resolution feature, but then he's back in the same blurry boat.
I think the most cost-effective route would be the Rift S. It's about the sharpest image he can get that the 1070 will actually be able to push. Even with the S, he will still need to run low settings for the 1070 to hold 90FPS.