You wrote: "his b2c idea" -- so you are making "his idea" a reality. Ethically, you shouldn't go "solo". If you were to break-up and take the idea, he might go

You wrote: "his b2c idea" -- so you are making "his idea" a reality. Ethically, you shouldn't go "solo". If you were to break-up and take the idea, he might go ballistic and sue you, etc. If you actually get the VC money, then perhaps you can get the VCs to see the reality and they might make favourable changes. It probably would be good for your track record to have a successful A-round, etc. Focus on what you are good at and don't spread yourself too thin doing tasks that should be outside your sphere. If you don't get the VC money and don't start generating revenue soon, then you really have to ask yourself whether you are giving your co-founder a free ride. Remember 50% of $0 is $0! That's the path for love of the product going sour, very sour.