New York recognizes legal separations, with or without an agreement; for your purposes, you would not want a separation agreement because that would just get incorporated into the divorce and make the divorce go that much smoother (since all the issues would have been resolved in the separation agreement).
You could file a Petition for spousal support, but you are not really living separate and apart from a financial point of view. If he is paying all the expenses, you would not get very much for yourself and since your son is living there, also and all his necessaries are taken care of by his father, you wouldn't be able to give the Judge a reason for your requesting child support.
Let me give you an outline you can work with:
Husband lives separate and apart and not in the marital residence;
Wife lives in the marital residence with son and she needs:
A. Spousal support;
B. Child support;
C. Husband to pay mortgage (if house), or rent if apartment
Husband has no grounds for divorce and cannot file Complaint in Divorce; only ground for him would be one (1) year separation and that is one year away.
New York is an equitable distribution state which means after the divorce proceedings are commenced, there will be a hearing on the distribution of marital property and if you do not agree, this can drag on for a while until a Judge steps in and takes over.
So there you have it!
Leaving positive Feedback, Bonus, etc., are always appreciated.
Thank you for allowing me to assist you,
ANDREA, JD, LL.M., Taxation
Member, NY & PA Bar
DISCLAIMER: The facts stated herein are information only and are not intended, nor should be construed as legal advice or legal opinion and No Attorney-Client relationship is formed by asking questions and receiving information; laws vary from state to state and to protect your interests, you should seek local counsel