1) The change fee is USD 25 - unless the ticket has been issued since mid December 2022 then the fee is USD 70
2) The refund fee is the same. Expired miles will be lost/not refunded.
3 + 4) No no-show penalty, i.e you can rebook after flight date (but within ticket validity)
I suggest you wait until 1 day before the flight date for possible schedule change or cancellation (which will allow you to rebook or cancel without fees). Then you call to cancel the flight but ask for the ticket to be put on hold for later rebooking/don't ask for refund. The ticket is valid for 1 year after issue date. Once you have found award availability for the new travel date you call TK to rebook (and pay the change fee + recalculation of taxes, fees etc).