Bruce, I hear your anxiety about in some way relinquishing "rights" to your son if you are not at 50/50 physical custody by January. I agree with others, though, that it is not at all in your son's best interest now to be at 50/50 by January given that you do not even have him for overnights yet.
A more realistic goal that I think would be in everyone better interest is to reach some sort of agreement/plan with your W by January that describes the progression via which you guys will reach a more equal parenting arrangement over the next few months. If there is a plan in place by January that shows an agreement to work towards something resembling 50/50, won't that be good enough? First you should progress to having an overnight and then a weekend, etc. before you progress to full-fledged 50/50. Maybe consult with some web sites or developmental psychologists that specialize in shared custody and working towards shared custody where there was mainly single parent custody at the outset (perhaps even with your W) to see what they recommend as developmentally appropriate.
The more your W believes that your concerns are with S and the overall family and not only with what is in your best interest, I am guessing the more receptive she might be. It may take some time for her to believe it to be true.
Me-53 W-49 D22,D18,D15 T-Since-12/2001 Married-9/2004 She Moved Out-5/28/2010 Piecing start-04/2011 Now-together Thread http://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2079304