I am not an expert on phals, but I had one given to me in August in spag, and by the time I repotted it, it had fewer green roots that yours does. It also had reddish leaves. I trimmed as much black as I could without killing more good root, sprayed the whole thing with antfungal stuff, let it dry a few hours. and repotted it. It recovered well in bark, and now has great roots and is in spike. Still has reddish leaves.
So, while I can't say if what I did is the "proper" way to handle it or not, it worked well for me. I do think you have enough root to hope for recovery. Good luck!