Itinerary before/after Kumano Kodo - Advice Needed

Hi everyone!

I'm visiting Japan for a second time this May but as a solo traveler, and I really want to do the Kumano Kodo trek. I've already found the official site and am looking to book this 6 day trip: https://www.kumano-travel.com/en/model-itineraries/6-days-E1-kumano-kodo-trek-nakahechi

My flights are booked arriving May 18 and departing June 1 2025 out of Haneda in Tokyo. I could use some advice:

1) Given the flights in and out of Tokyo's Haneda airport will bookend the trip, where would you schedule the Kumano Kodo trek in that two week window and which destinations would you visit before and after? It seems like maybe Osaka is logical starting point for the Kumano Kodo? The trek would likely end in Nachisan with the Kii-Katsuura station a short bus rise away. Where would you go next? I've already seen Koyasan, Itsukushima Shrine, Miyajima, Hiroshima, Kyoto, and Hakone.

2) The 6 day Nakahechi trek looked great to me, and I would opt for the abbreviated routes to keep the hiking down to 4-6 hours per day, but if you'd recommend otherwise or took a different itinerary or trail that you liked, I'd love to hear about it. Would also love to hear about any lodging or meal along the trail you liked in particular.

3) I read that the booking for the hike should be done 6 months out, but many of the accommodations don't seem to be available for booking yet on the Kumano Travel site within that window. Was that your experience?

I definitely appreciate any wisdom you have. Thanks all!