The IT 203 lists the federal income and the NY State amount. There are no questions about where the other income is being attributed to. Rather than how much is being allocated to Florida and New York, you would be asked to list the total federal income and the income attributed to NY. The fact that there is no Florida tax return, is irrelevant.
It seems like the employer may have treated your W-2 as if you lived in NY the whole time, and only worked in Florida part of the year. If that was the case NY would tax you on all the income earned and then credit you for the taxes paid in other state. This would not be accurate. In your situation, the W-2 state income needs to be split accurately.
