Hi Kid -
I've cycled all the roads you mention - numerous times.
First - elevation. You will be dealing with elevations in excess of 8000 ft.
Since you are a lowlander and just getting back into touring, I would urge prudence.
Also, high elevations can mean big weather swings in October -
You can be roasting by Lake Powell and wake up to a blizzard at Bryce.
Second, the climb up from Zion on Hwy 9 or Cedar City on Hwy 14 is tough.
Bikes are prohibited in the Zion tunnel, so you will have to beg a ride from a pick-up.
(The tunnel is alternating one-way, so there is stopped traffic from which to beg.)
There is another long, not-as-steep climb from Fredonia up to the Kaibab Plateau.
Third, at higher elevations there are forests, but at lower elevations shade is rare.
Exposed means not only rare shade but winds, too - - prevailing from the southwest.
Most of the time, riding towards the North Rim means dealing with a headwind.
(There are a number of fire closures in the region - check status.)
Also, shoulders are spotty to nonexistant. Traffic volume varies.
By October, tourist traffic is down, but still can be an issue in more popular places.
I see you are trying to do a loop of sorts.
Loops are very hard to do in southern Utah - very few paved roads.
If you are willing to do dirt, your options multiply manyfold.
US 89 between Page and Kanab is O.K., but boring.
Pic - Checkerboard Mesa in eastern Zion NP