I've never done a breeding contract so take my opinion lightly but I don't think you should have to compensate him if there is no clutch produced. It could have been that his female/s didn't take. I may be reaading that wrong since I'm really tired tonight....
X2 and the clutches should be split 50/50 even if you want just 1 you could sell the rest. or however you want to work it but to me 1 snake for you and all the rest for him seems completely unfair to me.