You may need a dynamic equity model that tracks the hourly inputs from each founder, and adjusts the equity split accordingly. Check out Slicing Pie . Even if you don't use exactly what the book prescribes, it will give you a good model and understanding for quantifying and tracking the various types of risks and contributions from your team.
Both of you have valid points. What I would suggest is put a dollar value to each hour, and have the option to pay either as cash, or cash plus equity or equity whenever the company's financial situation changes: maybe a funding event of $1m or more. You also need to give him equity for the position whatever it may be with the usual vesting period of one year cliff and for four years.