I get that he wants to stay there, but he would likely have to leave $6-8 mil on the table to stay. That is a huge amount of money for a guy who has earned less than $1.5 mil in his career by the age of 28. He was making less than $50k a year until he was 25, spent his age 26 season making about $100k until he got called up mid season for league minimum. For the last 2 years he has been making just over league minimum. Unlike most 28 year olds in this league, he is not financially comfortable for life unless he has been incredibly good with his money. A discount deal with the Hawks could very well mean that his career earnings as an NHLer are about $3-4 mil before taxes, escrow, agent/rep fees, etc. That's certainly nothing to scoff at, but it isn't the monopoly money wealth that most people associate with a pro athlete. Goalie is such a fickle position that there is always a chance that a good 28 year old is out of a job 2-3 years later.
Realistically, the Hawks don't have the space to give him much more than he is making now ($585k). They currently have $2.7 mil in cap space (if the cap doesn't rise), but that is before any bonus overages. Panarin hit all $2.575 mil of his bonuses, Campbell hit his $750k bonus, Kempny got $250k of his bonuses and Forsling got $95k. That's about $3.7 mil in bonuses and the Hawks ended the year with $10k of cap space. So they are looking at over $3.5 mil in bonus overage cap hit and currently have negative cap space assuming a cap the same as this year.
The cap is going to go up, but we have no idea by how much. Assuming similar growth to the last couple years (and the players using their escalator), we are looking at a cap of about $75 mil. Assuming that, the Hawks have about $1 mil in space with 20 guys on the roster. A few of the guys projected on the roster right now won't be there, so realistically this number is more like $3.5 mil with 16-17 guys on the roster. Even if they get Vegas to take Kruger, you are looking at about $6-6.5 mil to fill 6-7 roster spots (including finding suitable replacements for Oduya and Campbell). Remember, Panik is an RFA and he had 44 points this year while making $875k. He is due a raise or will need to be moved. How do you give anything close to a fair contract to Darling with so little cap flexibility? Even an AAV of $1.25 is probably pushing it for the Hawks and he should be able to find another team to give him $3+ mil on a 3 year deal. I do believe he would take a big discount to stay in Chicago, but usually a discount for a late 20s player is 10-15%, maybe 25%. He would have to take a 65% (or more) discount just to get into the ballpark of what Chicago can likely afford unless they move a big contract.
I don't see the Hawks being able or interested in moving Crawford. The details of his NTC are unknown, but even a list of 7 teams he can't be traded to would drastically reduce the Hawks' ability to get anything of value for him. How many teams are looking for a $6 mil/year starting goalie without needing to send a few mil in salary back? Assuming Crawford wants to stay and puts those teams desperate for a goalie on his list, how does Chicago move him for close to fair value? Unless the Hawks believe losing Crawford for peanuts is better than losing Darling for nothing, I don't think moving Crawford is realistic. Given the contract they gave Crawford, his performance in the first half of that contract and his known playoff track record, I don't see them moving Crawford at a discount just to save a few million in goal.