If he loses Learning Resources, Inc. v. Trump (the Tariffs case in front of SCOTUS) then he has no power with which to negotiate. Because, as you suggest, his military is unwilling to execute the unlawful orders to seek conquest without a declaration of war.

So that might indicate some of the apparent urgency to make this happen now before SCOTUS rules.

Unfortunately a lot of damage is already done, even if we walk it all back our allies will no longer trust us - nor should they.