Promo awards cannot be changed or cancelled, apart during the flexible period due to Covid, but this is ending end June. As your ticket is for July, you are back to the old rules : no change possible. If you cancel, you loose the miles.
As you said you already took the ticket, it’s too late to change the date.
The part in cash, corresponds to all the taxes and the various carrier-imposed surcharges (originally introduced as fuel surcharges many years ago but remained after fuel came back to normal prices).