Your batched stats could be examined if starting and relieving were intermingled enough, but otherwise, they are relatively worthless to cite. Rookie pitchers develop.

As for the overall question I don't have enough information to make a recommendation to be honest. I would hope the Mets staff would.

Sure his relief numbers look better, but (a) most of his starts came early in his career, before he was really ready for the bigs, and (b) recently his relief appearances have been lousy.  So what are we to conclude?  That he will somehow magically become effective again if allowed to start?  Or that his period of dominant relief pitching was an outlier and that he is reverting to his mediocre norm as the league figures him out?  I'm leaning toward the latter, but I'm just a fan, so what do I know?  But if by some miracle I'm right, the solution is obvious--trade him now while there's still a market for him.