If he had exercised his NBA out clause then he would no longer be a contracted Adelaide player. So SEM could still have signed him unless the 36ers had got him to sign a contract for his return to the NBL, but he would have been under no obligation to sign that.
Yes, and he could worm his way out of any contract anyway but he's far less likely to do that, and SEM are far less likely to approach him, if the club has a solid relationship with him or some form of arrangement.
Like you said, he's a player you build around. Not a player you go miles out of your way to offend, and offend a bit more, and then completely embarrass yourself offending yet again.
He didn't have crazy expectations. Just didn't want to be lowballed relative to teammates, ignored and then harassed legally.
If you can't compete financially, you make sure your player doesn't start hearing offers, that rivals aren't shortlisting them to approach because they assume they're happy, etc.