Hi D --
First of all - in mediation, you and your ex would discuss all of your respective thoughts/feelings about this issue. It's clear that you will have some transitional expenses, and transitional adjustment. Maybe he initiated this - in which case he may be feeling guilty, and be more open to helping you through this transition.
All of these things would be explored, in order to come up with a settlement that you both can live with.
Now, to answer your questions about the law:
Alimony in NY is no longer called alimony - it's called "Rehabilitative Maintenance." The goal of maintenance, as stated in the statute, is that everyone should become self-supporting.
There are 14 factors that a court would examine - and they add up to, basically, your life - your relative ages, earning history, earning potential, educations, whether one person gave up a career, or career growth, to care for children or contribute to the other person's career - and the lifestyle enjoyed during the marriage.
There is no formula - which means that spousal maintenance is one of the most hotly-fought-over areas of the law. It's highly discretionary. Some judges are generous - others not. It becomes the "luck of the draw" (as are so many things if you take it to a judge).
It sounds as if there is a big difference in your incomes - but it also sounds as if you have had a short marriage. Were you self-supporting before the marriage? If so - perhaps you would be expected to resume your pre-marriage lifestyle.
A "rule-of-thumb" that is used in the courts is that maintenance should last only for 1/3 to 1/2 the length of the marriage - which means that - for a 3 year marriage - the most you could expect would be 1 to 1 1/2 years of spousal support.
If you had become seriously disabled, such that you could not be expected to be self-supporting in your future, there would be a different result.
Best of luck to you, going forward,
Rachel