EA: Since is does not add up to 100%, we should assume the "lost" % is oxygen.The % data allows one can get the empirical formula = C₂H₅NO. By checking the MW of the empirical formula (2x12) + (5x1) + 14 + 16 = 59, we know that the molecular formula is also  C₂H₅NO.
Here is a list of possible isomers :

The pairs of geometrical isomers are adjacent to each other in the figure and are named as E- or Z-.
Any other pair of compounds would be constitutional isomers.

Resonance.... Well only those structues with pi bonds can exhibit resonance. The forms shown above would be the major contributors and any with charge separation would be less important.