I'd advise not cutting it back. Just wrap the netting around the Fothergilla and attach to the Buddleia as well. The deer are not going to duck under the Buddleia to get to the fothergilla. They can't see the black netting, and feeling it but not knowing exactly where it is is very unpleasant to them since they can't tell whether they might get caught up in it.

It would take at least that long to grow back.

Yes, cut them now just as you said but do one more thing: Poke a hole in the ground and insert these cuttings and water them. Some will root and be new plants for next year.

Read on one of the iris societies that one should cut the flower stalk once it bloomed and to only cut off those leaves that are damaged. I suppose if all the leaves are damaged, then do what Liz does.