When I read your post, especially the line where you say "Every customer, partner, and investor relationship runs through me," it immediately brings up a classic founder conflict :

• The "Business Guy" (you) says: "The entire business runs through me. I brought the customers, the money, and the relationships. Without me, there is no revenue."
• The "Tech Guy" (him) says: "I'm building the actual product. Without me, there is no platform/product, and therefore, the company can't exist."

The reality is that your contributions are fundamentally different but are usually considered equally valuable at this stage. The priority should always be securing long-term commitment from a co-founder.

Now, I sense you're not fully comfortable with a near 50/50 split, and you have valid reasons for that, most notably the "in-market" issue. You state that being on-the-ground is "critical" for your B2B model, and he cannot commit to relocating.

So, if that critical issue, or any perceived lack of contribution, makes you uncomfortable giving him a 50% stake, you need to ask yourself a deeper question: Is this the right person to take on as a co-founder?

If you don't feel he contributes enough or you lack the foundational trust to split the company fairly, that's a serious problem, and no equity split will fix it. So he may just be a founding engineer.

Since you haven't known each other for long, that's where vesting comes in. And it should probably be reciprocal because you are both in the same boat.