Drain syrup from pears and set syrup aside for later use in caramel topping.
Layer bread and pears in 8 (1-cup) mason jars alternating layers.
In a large mixing bowl, whisk together eggs, milk, sugar, 3 tablespoons rum if desired, vanilla, cinnamon, and salt until well combined. Spoon over pear and bread in mason jars. Using the back of a spoon, press lightly on bread so that the bread soaks up some of the liquid.
Place mason jars in slow cooker. Pour water into bottom of slow cooker (being careful not to get water into bread pudding) so that water is about 1-inch deep.
Cover slow cooker and cook on low for about 3 hours or until bread pudding is set and a knife inserted into middle comes out clean.
Meanwhile, mix together caramel, 2 tablespoons of reserved pear syrup, and remaining 2 tablespoons of rum if desired in microwave safe bowl. Microwave on high in 30 second intervals until warm.
Top bread pudding with caramel sauce, whipped cream/topping, and nuts as desired.
SNAPPY TIPS: Do not lift the top off of your slow cooker very often if at all so that the steam can help cook the bread pudding.SNAPPY SUBSTITUTIONS: Instead of cinnamon you can use any kind of spice or spice mixture. Instead of caramel, real maple syrup is also great. Instead of rum, you could use orange juice or omit.