Okay, ill will try to help the best I can from what I read. So, If the grid you are using is 30x45(1,350 squares) and the small gene is about 4,500 bases, I would say you need at least 4 pages.
1350x3=4,050 bases
1,350x 4= 5,400 bases
It would be good to have the extra room to just in case you need to add anything else. I say this because it sounds like there could be more added. So I hope I helped in some way, and please correct me if I'm wrong.