I suspect that this might be part of the problem, he has mentioned that he would like to re-negotiate the equity split. However, I feel like giving him a larger proportion of the company to solve a motivation issue is not the right thing to do.

Well, personally I'd never start a partnership with someone that wasn't even. If they're not worth half they're not worth partnering with.

There are exceptions: if I invested in the company I might end up with more equity based on that investment, but it would still start at 50/50 on day one.

No one feels bad if you put in $500k to get an extra 20%. But just arbitrarily deciding one guy gets an extra 20%? That's going to gnaw at you later.

You said you put in 70% of the money and he put in 30%. Is he willing to match your contribution to get himself up to 50%?

not really possible, he doesn't have the money.