I have the same GPU and the same settings except I am using in game v-sync and not forcing it through RadeonPro. I am also using borderless windowed mode instead of fullscreen. I get infrequent stuttering when it's probably streaming in new data, but it doesn't happen often enough for me to complain about it. A solid 60fps 90% of the time. Are you saying that once it hits 30fps it stays there? Because I had the same problem with Far Cry 3 until I switched to borderless windowed mode there. Also try changing "flip queue size" in RadeonPro to 1, this fixed stuttering in The Witcher 2 for me and I'm pretty sure I have it set to that for Infinite, too.
it will go back up to 60