Break it down into the three roles that are described here, co-founder, investor and employee.
You are both co-founders. He is taking considerable risk along with you and neither the product nor the market have been proved yet. Split the founder's equity 50-50 with identical terms.
Your investment, along with the rest of the F&F money should be written up as convertible notes. You will get that money back (plus interest) in the form of cash or stock (at a discounted conversion) when the company succeeds. Obviously, since he is not an investor, your co-founder won't get any of that.
Finally, you are both employees. Since you are also both co-founders you typically don't issue additional equity. However, if you both feel it is the fair thing to do then you could issue stock options to yourself, as the CEO, to make up for the salary cut. 5%, vesting over 4 years, would be typical for a CEO (with salary), but then even a fully-paid CTO would expect to get 2-3%. All things being equal, and assuming you don't both take employee stock options (because it is just more paperwork) I would say that your 50% salary cut is worth a couple of percent in options, at most.
The big variable here isn't your personal stake in the company, it is the success of that company. It is important that all parties feel that the split is equitable and they are full engaged in the process. Treating the guy who has chosen to join you at this early (and very risky) stage as anything less than a cofounder could make the difference between him making a superhuman effort to help the company succeed and treating it as just a job. Deal with the investment and compensation issues seperatly.
Oh, and take the hit to pay a decent attorney to get all this written up (corp docs, co-founder docs, stock plan, convertible notes) and filed properly. A few $k now will save major problems down the road and make your company much more appealing to investors.
Good luck with the startup :-)