Combine 1/2 cup sugar, cinnamon, and salt in large bowl. Add peaches, blueberries and lemon juice and toss gently to coat. Let stand 30 minutes.
Meanwhile, stir remaining 1/2 cup sugar and 1/4 cup water in medium saucepan over medium heat until sugar dissolves. Increase heat; boil without stirring until syrup is deep amber, occasionally swirling pan and brushing down sides with wet pastry brush, about 11 minutes. Remove from heat. Add butter and cream (mixture will bubble vigorously); stir caramel until smooth. Strain juices from peaches into caramel; cool to lukewarm. Preheat oven to 375°F. Mix the caramel and flour, and then add this to the peaches and blueberries; toss gently.
Take a handful of flour sugar and coat the bottom of the pie pan. This will soak of some the juices from the fruit to keep the bottom of the crust from becoming soggy. Then, transfer fruit filling to crust, mounding in center.
Arrange 6 dough strips in 1 direction across top of pie, spacing apart. Working with 1 strip at a time, arrange 6 more strips in opposite direction atop first, lifting strips and weaving over and under, forming lattice. Gently press ends of strips to edge of baked bottom crust to adhere. Trim overhang. Brush lattice strips (but not crust edge) with egg yolk glaze. Sprinkle strips with cinnamon sugar.
Bake pie 35 minutes. Tent pie loosely with foil to prevent overbrowning. Continue to bake pie until filling bubbles thickly and lattice is golden brown, about 25 minutes longer. Cool pie on rack.