It would not be called alimony, rather it would be either spousal support or, in the event there is a pending divorce case, it could be APL (alimony pendente lite). In either case, if you move out, she can go to domestic relations and file a spousal support claim and the case will be scheduled for a support conference. If support is awarded at the conference, the effective date will the date she filed the application. Therefore, if she files on May 1st, but the conference does not take place until June 1st and an order is entered at time, you will be one month behind in your support obligation. Depending on the type of disability your wife receives, it may or may not be included when calculating her income. Generally, spousal support is 40% of the difference between your two incomes. In other words, subtract her monthly income from your monthly income and she gets 40% of that amount.
The above answer is intended solely for general informational purposes and does not create an attorney client relationship. You should consult with an experienced attorney regarding all of the details of your particular situation before taking action.
If a divorce complaint has not been filed it is called Spousal Support. If a divorce complaint has been filed it is called Alimony Pendente Lite. The amount is based upon a formula considering what you earn and what she earns. If you do not move and pay all the household bills then she cannot file for spousal support. She would then be forced to file a divorce complaint and you can then move the case along more quickly. You don't have to voluntarily leave. Just don't cause any problems that would allow her to file for a PFA.