Place raisins in a medium bowl. Heat rum in small sauce pot until it begins to simmer. Remove from heat and pour over raisins. Let sit for 2-3 hours until rum has cooled to room temperature and raisins have plumped up. Strain raisins and discard rum. Set aside.
In a large cup, add warm milk, 2 tsp sugar, and active dry yeast. Stir to combine. Let sit for 5-8 minutes until yeast has activated and mixture is foamy.
In a large bowl, whisk together flour, cinnamon, and sea salt. Set aside.
Pour yeast mixture into the bowl of stand mixer fitted with a hook attachment. Add remaining sugar, cooled melted butter, lightly whisked eggs.
With the mixer running on low speed, add the flour mixture in three additions. Once all the flour add been added, increase speed to medium. Continue to mix until dough comes together to form a smooth, soft ball.
Remove from mixing bowl and transfer to a lightly oiled large bowl. Cover with plastic wrap and let dough rise in a warm area for 1 hour. Punch dough down and divide the dough into two equal parts.
Mix together filling. In a small bowl, combine softened butter, dark brown sugar, cinnamon and orange zest until smooth.
Working with one piece of dough at a tie, roll dough into a rectangle about 9"x13" in size. (Have the shorter side of the rectangle facing you.) Sprinkle half of the rum raisins over the dough. Using the palms of your hands (or a rolling pin) gently press raisins into the dough. Take half of the filing mixture and spread it evenly over the raisins and dough.
Roll up the dough tightly and pinch the seams together. Tuck the ends of the roll under. Place loaf seam side down in a lightly greased 9"x 4" loaf pan. Cover with plastic wrap and let rest for 30 minutes. Repeat with other half of dough. Preheat oven to 350 degrees F.
Whisk together egg wash. Brush egg wash over the top of the loaves. Bake for 35-40 minutes until the tops of the bread are golden brown. To ensure doneness, check the internal temperature of the bread using a kitchen thermometer. The internal temperature should be above 185 degrees F. Let cool in pan for 5 minutes before unmolding. Allow to cool to room temperature on a wire rack. Do not slice into bread until it has cooled down.