I like your optimism, but no, those 4 moves won't free up nearly that much space. Those four players currently combine for a $61.841MM cap hit. Cutting JT and James will save $13.941MM. But Suh and Tannehill will still be on the team and their cap hits will be significant. Restructuring won't be able to reduce their cap hits from $45.9MM down to less than a third of that. And whatever they do will just make their 2019 situation worse.I really don't think they intend to trade him. Tag and trade is technically not allowed anymore by the CBA I believe, though of course teams can try and skirt around it by claiming they intended to keep the player but got an offer they couldn't refuse. Still it's probably more trouble than it's worth for what they could get for landry at this point.
Regarding cap space the fins haven't done their cap clearing moves yet, which are expected to be substantial. They're going to try and restructure Suh and Tannehill as well as likely cut Julius Thomas and Ja'wan James among others. Those 4 moves alone could free up 50-60 million in cap space.
I'm guessing those four moves free up maybe $25-30MM.