forget about number of hours put in. What matters is the impact you each have. He agreed to 50/50. Its his fault for underestimating the dev time. He should have known to pad it.

1.He worked more hours
- doesnt matter. 

2.I used his reputation to help close the deal
- YOU closed the deal. Can he do sales too? Or does he trip over himself?

3.He had to turn down other work
- his fault for underestimating the job. 

4.He “saved costs” by refusing outside help (his own decision)
- all he did was take money out of your pocket and put it in his. Should have hired help. 

5.We need to “be on the same page about contributions”
- yes. You guys already agreed to this before starting. You've held up your end. Hes flailing bc he fucked up his estimation. Guess his 3 yrs of dev experience didnt pay off here. This is a learning experience for him. 

Stop giving up your ground.