I talked with Westport Yarns finisher as to how best to block cotton lace. She was (of course) extremely helpful and suggested I pin it out dry and then place a wet towel over it and let it sit like that overnight. In the morning I removed the towel (opened a window) and let it dry.
I still couldn't bear to take out the lifelines. Hanging on to them like a security blanket.
It blocked out beautifully, I'm very happy with how it came out. Now I'm left with finishing, weaving, sewing, etc. I took a deep breath and removed all the lifelines except for one. No real logic there.
When it's all finished, I'll share a picture of the final piece.