Are you truly using a collaborative agreement, or are you simply calling it collaborative because you are using a mediator and trying to be cooperative? Did you sign an agreement that should negotiations fail these Ls won't represent you in court?
Also, in FL, I believe the sharing percentage is based strictly on overnights. I realize that you need a 24/7 plan for your son but the sharing percentage can seem different than reality. For instance, you can have S4 from 8am to 8pm, he spends the night with H, and then you get him back at 8am the next morning. That's not 50/50 that's one overnight for H and none for you. Is that the way your L has explained it to you?
