Right now Puigdemont is backed against the wall. He has two options:
1. Declare independence, knowing full well that it likely will be useless given they don't have any way to exercise it and no one will recognize them. As a result, he will likely end in prison and the conflict will escalate, given that the people will not take it lightly. More business will leave Catalonia. Who knows where it goes from here.
2. Not declare independence. In that case the most radical pro-independent sectors will likely want his head on a silver platter. The pro-independence coalition will be split between its most radical sectors and the more moderate ones, likely leading to new elections.
I definitely wouldn't want to be on his shoes, but he knew full well what the job entailed when he took it. Personally I think he'll go for 1, mainly because if he has gone this far I doubt he will not take one more step, even if that means prisons for him.