What causes these different behaviors in my amplifier?
I think I figured out what was going on. My stackup was slightly different than the skyworks eval board, but not by much. I calculated that it should only change my CPW impedance by a few ohms. But I realized that I neglected to order high Q passives. Once I repopulated the board with high Q inductors and capacitors, the oscillation went away:
https://www.youtube.com/watch?v=Fq7UKLlVpa4

The difference GJM and GRM series from Murata really really matters! My gain is still not quite what it should be, but I'm going to fab these boards again and put a lot more ground via stitching in (another thing I forgot to do) and see if that improves performance at all.