Figuring out Nutritional Information

My mom makes AMAZING chocolate chip pumpkin bread, so I've been trying to figure out the nutritional information so I can eat it without feeling like I'm consuming 1000 calories. I've calculated it using an online recipe calculator and using various nutrition labels from online (I don't have the bags for some of the raw baking items like the four and sugar) but I keep getting completely different values (anything from 100 calories to 400 calories per serving).

The recipe is:

3 cups flour
4 eggs
2 cups sugar
2 cups pumpkin
1 cup oil
2 tsp baking soda
2 tsp baking powder
1/2 tsp salt
1/2 tsp cinnamon
1 cup semi-sweet mini chocolate chips

I'm trying to figure out the OVERALL nutrition information for this recipe since the serving size varies depending what size loafs we make and how we slice it. Any help would be greatly appreciated.