still unclear about rail passes

I have read the information about the rail passes but still not sure what's best for my itinerary.

My 16 day itinerary is fly into Osaka and go straight to Kyoto ( I can see I should take the Haruka express train for this). 5 nights in Kyoto. I night Hiroshima. I night Miyajima. 2 nights Osaka. train to Kii-Tanabe for 6 day walk and then train from Kii-Katsuura back to Osaka.

Thank-you for any advice.

No pass is gonna pay off covering the whole trip. Long trip with short duration journeys.

Get a 5day hiroshima-kansai pass for your Hiroshima leg. As this is for 5 days, you plan for what works best for you the other non Hiroshima days.

All other days I would be just getting single one way tickets.

Hi!

If it were me, I would probably do:

One of these passes to get from KIX to Kyoto: https://www.westjr.co.jp/global/en/ticket/icoca-haruka/

It's a discounted Haruka ticket+ICOCA Card. If you don't already have one, the deal is quite decent and you can use the card to get around Kyoto.

Since you are only spending 2 nights in the Hiroshima area and then 2 nights in Osaka before heading to Kii-Tanabe, I would probably get this pass:

https://www.westjr.co.jp/global/en/ticket/pass/kansai_hiroshima/

The 13,500 yen cost will pretty much be covered just in your Hiroshima round trip though do note, you will need to take a local or limited express between Kyoto and Shin-Osaka. It's not as bad as it sounds, as if you had a general JR Pass, you would only be able to take the less frequent Hikari and Kodama, so by that point taking local or limited express is not going to slow you down that much and chances are high you would be changing somewhere as is. The pass will also cover your trip to Kii-Tanabe.

Coming back I would just pay out of pocket for a Kuroshio to Wakayama and then take the limo bus from Wakayama to KIX. They run once an hour, take 40 minutes only and cost only 1150 yen. I would probably spend my last night in Wakayama just to be safe unless your flight is very late in the day.

Enjoy!

Your confusion is not surprising - it's very hard to make any Kansai area pass pay off without some long distance traveling in a short time.
I did notice that you didn't mention Nara at all - you'd be doing yourself a terrible disservice if you skipped that wonderful city. Nara Park is one of the best places you could ever visit in Japan.
https://goo.gl/LfvWnL

I'd also say you could safely pull a day off of Osaka and go see Himeji - it has the best old castle and Kokoen Garden is beautiful.
https://goo.gl/65ZtRi
And if you are putting in both a day for Hiroshima as well as Miyajima, you should have enough to see the sights of the area. Don't just see the Peace Park - the city has a lot more there and while sadly many just see the park and leave the city, the Shukkeien Garden, castle, Mazda Museum, Okonomi-Mura, and gorgeous Mitakidera temple are uncrowded and a real delight.
https://goo.gl/fAz4ax
Try to see the Itsukushima Shrine on Miyajima at both high and low tides - it's truly wonderful.
http://www.tides4fishing.com/jp/hiroshima/itsukushima
https://goo.gl/g8HWjh

Good luck.