Ooey Gooey Peanut Butter-Chocolate Brownies

3/4 cup fat-free sweetened condensed milk, divided
1/4 cup butter or stick margarine, melted and cooled
1/4 cup fat-free milk
1 (18.25 ounce) box devils food cake mix
1 large egg white, lightly beaten
Cooking spray
1 (7 ounce) jar Marshmallow Cr