Well C&D would be the only reasonably way to start even if one was going to sue. It's frowned upon to just dive on in with litigation. The semantics thing would get laughed out of court, not that this would get to court in a billion years, since they carefully included an "entire agreement" clause as most contracts do, and they specifically differentiate between a "Track" and a "sample", because they also have complete tracks as something else they sell, I guess. Oops.That certainly would be true depending on the nature of the lawsuit. But if Splice were sued, they could argue semantics, saying that they use "samples" as a blanket term for their loops, which they may redefine in court as compositions. So I wouldn't consider anything open and shut. If I were Spitfire and felt Splice were violating my EULA, I would send them a cease & desist letter. If it didn't work, I would consult a legal expert to determine the plausibility of litigation.
"Track means any User Content you Post that is a musical work or sound recording...".
That usually goes a long way.
Either way, Spitfire should go at them. It's not legal.