Crush 50 wafers to form fine crumbs; place in medium bowl. Melt 1/3 cup butter. Add to wafer crumbs; mix well. Press onto bottom of 9-1/2-inch tart pan.
Crush remaining wafers coarsely; place in medium bowl. Melt remaining butter. Add to wafer crumbs along with the nuts, sugar and 1/4 tsp. pumpkin pie spice; mix well. Spread onto bottom of shallow pan; place in oven along with the crust.
Bake crust and nut mixture 10 to 12 min. or until lightly browned; cool.
Beat cream cheese and pumpkin in medium bowl with mixer until blended. Add dry pudding mix and remaining pie spice; beat until blended. Gradually beat in milk; spread over crust. Top with COOL WHIP, spreading to within 1/2 inch of edge. Refrigerate 4 hours. Meanwhile, break cooled baked nut mixture into smaller pieces; store in airtight container until ready to use.
Remove tart from side of pan just before serving; top tart with nut mixture. Microwave caramels and water in microwaveable bowl on HIGH 1-1/2 min. or until caramels are completely melted, stirring after 45 sec. Drizzle over tart.