Do you intend to walk on the road, or on the Lycian Way ? - By the Lycian Way route Faralaya to Kabak the distance (to Kabak beach) is 7.6 Km and should take about 2 to 2.5 hours (depending on how fast you walk and what you are carrying). I am unsure how far it is by road possibly approximately 5.5 Km.
If you go by the Lycian Way the route is not too bad a bit of a climb up as you come out of Faralaya village, but then flattens to meadows and then down hill into Kabak, then as you say a down hill section from the village of Kabak to the beach (but the path is good), a little bit of a climb then to get back up. You could always get a lift up or just stop your walk in the village and have lunch (The views are still stunning !, The Olive Garden restaurant very good).
I think the Dolmus goes back every hour or so (from the village).
I hope this makes sense, if not please ask further questions, but as previously mentioned take care with the heat at the moment and carry plenty of water !. Enjoy