Well darling will be in for a HUGE pay-day as a starter somewhere next year.
I don't think it is going to be as big as you are thinking...and don't be surprised if it is as a starter for the Blackhawks. Cap Hell might make that move happen.
I don't know how well Darling would hold up either, but I can assure you that it has been spoken about at some length as a possible option. A lot would have to happen (As it does for most trades) but it is certainly a possibility. The cap forces teams into decisions like these and it wouldn't surprise me one bit.
At low-ball You can assume Darling will get a min of 2MAAV--this is comparable to Emery's 2014 deal.
As for the possibility of moving Crawford, his L-NTC, NMC, and the UFA goalie market this summer might make that difficult. He *has* to be protected in expansion and is under no obligation to waive his NMC. I believe his L-NTC is something like 5-6 teams he'll accept a trade to--but I read that awhile ago so I could be wrong and if his list is LA, NYR, Washinton, Boston, Nashville, or Montreal (all teams with an expensive netminder signed for the duration), he might be immovable.
Note...not impossible, but difficult. Plus, given that you're looking at a netminder with hardware Stan would have to be guano to part with him for something like a 3rd. Ergo, something is going to have to come back and likely it will be someone on the roster and then some (ditto for all of the core in a potential move).
I have faith that Darling, if tapped, can be effective as long as our skater core doesn't play like last season. The thing then would be finding a reasonable take for Craqwford and right now only Calgary comes to mind. But, why would Calgary give up assets to take on Crawford when they could have Darling, Bishop, Bernier, Mason, Miller, etc. for free and possibly cheaper?
That will come into play.