[helen842000]

As defensive as he'll probably be you've got to have the conversation.

Make it about the future not about the past (we all know how tiring "I did this" - "no you didn't" conversations can get)

Sit down and say - look we're doing great aren't we! This is the point where we need to decide how we're moving forward. Options are he matches your work hours - you're both at full time, you both keep 50/50. He keeps his job and scales back to 25/75. OR you match his working hours (i.e very little) and you're then free to pursue whatever else you're interested in.

Make it clear though that you're really keen to work full time on the project and you want him to do his bit.

It seems he's on the greedy-train seeing how long he can last with a full time job and 50% of the lucrative project income. Talking about the past will probably just cause arguments. Make it like now is the time to make the right choice.