Do leaves have a waxy cuticle on the lower epidermis too?

no because it has few stomata especially is used in xerophitic plants because it has to respire . the waxy cuticle helps in reflecting the light intensity and helps in controlling the transpiration process

No, the waxy cuticle is only necessary on the upper layer to allow for light to pass through the leaf however prevent unnecessary water loss through evaporation. If you're interested the lower epidermis has holes called stomata (singular stoma) which are controlled by highly specialised cells called guard cells, through which water and other products of photosynthesis can escape. You probably already knew that last bit anyway but oh well! Hope it helps!