Is the only way forward to fire some of my already established players to allow for that salary?
Honestly, and I'm not just saying this because you're one of my new division rivals ... Yes. Given that the new NT guy you got is the only player you now have under the age of 34 (with the exception of the new draftees), you should probably look to blow up the team and start again, especially since you're so low on cash right now.
Just don't try and tank harder than me this season, I want another number 1 draft pick. :)