Your outlook is not one that I currently relate to, but I certainly have had similar restrictions on myself and my lover in the past. For me, this idea of getting equal time, having fair priority in each others lives, making sure I am loved *as much* as their other lovers is not applicable. Relationships are fluid, the level of closeness evolves due to a myriad of factors. This is true in a monogamous relationship as well as a polyamorous one, the primary difference is the addition of another relationship as a complication and removal of lying as a solution.
I might suggest that you empower your boyfriend, appreciate that he will have this girl as steady company, hope that their relationship blossoms into something beautiful, and love him with everything you've got. Treat their time with respect and make your desire to spend time with him known in no uncertain terms. Clutching onto this idea of making sure you get your fair share will almost certainly turn this polyamorous relationship into a previous relationship.
My recommendation about you telling them how many nights they can sleep together is... consider that their relationship is their own and is, quite frankly, none of your concern.
Originally Posted by Tonberry
Even if the relationships were to evolve at different rates, you can't rush yours and potentially damage it just to stay parallel to theirs. They're different relationships, so try to follow your own rhythm and you'll get there.