I feel very similarly. I am currently choosing between two private schools who do not offer me much money (and have extremely expensive tuitions) and two public schools that have policies about not funding MA (but are considerably, considerably lower than the first two.)
Just as my two cents, I think that there's nothing wrong with deferring entrance. It will give you a chance to get out in the real world, away from academia. You may get a better sense of what museums, galleries, or institutions are looking for, and what you really need to do to progress to the job you want (What kind of job do you want?). You can also re-apply to PhD programs, or apply to the Syracuse PhD program in that year with more life experience and a better sense of what you want to do in your research. Also, if you are accepted to more programs next year, you can use that and whatever money another school may offer you as leverage.
Although it is currently really close to the decision date, you should definitely contact Syracuse! Tell them about your awards, and drop some information about your thesis in conversation. Then ask about the financial situation. It can't hurt, and there's a chance they may reconsider your funding based on new information.
Fair warning though, MA Art History programs are often sparsely funded. Student debt is a serious consideration. This is a question that I've wanted to ask of the forum for a while- what kind of student debt is everyone in (roughly speaking)? Is that putting anyone off their dream graduate school? Also, is it true that private school Art History graduates make more money than public?