Question: Sometimes I don't succeed in finishing the meal I was eating. May my husband finish it in my place while I am Niddah?
Answer: If your husband maintains the customs of Sephardic Jews he may eat what you left on your plate or the leftover bread that you didn't finish, since according to the Sephardic custom one may only not drink the leftovers of a cup which his wife drank from when she was Niddah. However regarding leftover food a husband may eat it, as explained by Rabbi Ovadia Yosef in his book Taharat Habayit part 2 page 125.
If your husband maintains Ashkenazic customs, he would be forbidden from eating what you left on the plate or your leftover bread. However if he transferred the food from your plate to another plate he would be allowed to eat from it, since when one transfers the food or drink to another utensil, the husband may eat or drink what his wife left over as explained by Rema Yoreh Deah 195: 4.