What is a Fair comission when the developer becomes a realtor

Well folks here is one for open discussion.  I ran across it by accident when a client asked if I was aware of project X.  I said no and he said you need to meet Jim, the developer.  Therefore, since he was driving I came along.  I was introduced to the Developer and we spent nearly three hours talking about his plans, dreams and so forth.  Of course, I had offered a few comments but truly was impressed with his concept and the land itself.  Near the end of our conversation, Jim (the Developer) asked me what I did.  I told him I was a broker and assured him I had not come to his project to worm my way in.  I simply was riding with my Client who he knew and…well here I was.  He smiled asked me for my card and said he liked what I had to say and would be in touch.  You see two other brokers who were prospecting have also approached him and he had not been impressed for neither had gotten him anything he had asked of them in their initiated contact.  Well over the past year I have dropped in a couple of times a month, met his son, who is a sharp person and who ultimately been the project manager.  Early on, I had mentioned that the son should get his license as a Realtor.  Well, he has and now here is my problem.  The Son wants to hang is license with us but here is the catch.  He wants an 80/20 split on the listing side for this project since he is bring the listing on a 126-lot project as an exclusive.  The problem is that he admits that he will be up to his neck with the details of the project and will not be able to devote 100% of his time to working the sales side.  Which means someone will have to be doing a portion of the paperwork for him.  We have offered him a 70/30 split on the listing side and a 65/35 split on the selling side.  If it an in-house sale the total commissions would be 7% but a co brokered situation it would be 8% of which he’d get ½ of 70% the balance going to the co-listing agent.  Therefore, my question is this anyone have any better suggestions.  We are still negotiating so everything is subject to change.