Yes you DO have a contract.

You and the other side definitely agreed on the material terms of the deal clearly expressed in emails going back and forth, but you left undecided some relevant but not absolutely essentia items, thinking you all can decide on that later. Do you have an enforceable contract? YES.

According to the Firast Dept. Appelate Division in Aiello v. BURNS INTL. SEC., 110 AD 3d 234 - (1st Dept. 2013):

"[a] contract does not necessarily lack all effect merely because it expresses the idea that something is left to future agreement" (Four Seasons Hotels v Vinnik, 127 AD2d 310, 317 [1st Dept 1987]). The court shall enforce a contract if the parties have completed negotiations of essential elements, even when "the parties have expressly left ... other elements for future negotiation and agreement" (id. at 317; cf. Conopco, Inc. v Wathne Ltd., 190 AD2d 587 [1st Dept 1993])