It looks solid except that I don't think it's wise to spread your focus among two schools. I think it might be easier to drop enchantment and free up a couple of feats.
That would mean grabbing Improved initiative at 3 since you want to be debuffing ASAP before your heavy hitters move in.
With two feats left what else is there? I'd honestly consider grabbing Whip Proficiency wiht this build. Why? Mainly because it's a dex based weapon without weapon finnesse that you can stick spell storing on. Sitting back 10ft-15ft. in an area of darkness and periodically dropping a harm on someone is a very good way to deal damage without fear of reprisal.
With one feat left I'd consider Umbral spell to add an additional darkness effect to your debuffs.
That was a mistake on my part. My brain went back to the 3.5 days when the whip was resolved as a ranged attack. Still, it's an okay option. Hitting opponents shouldnt be too hard when its dark, foggy, and they're blind with inspire courage going.
If not consider that a free feat to do pretty much anything with.
The suggestions so far have been quite good, and your plan of going full cleric is probably the "best" in terms of optimization. Just a few ideas and possible dips to add to the discussion, since I love the class and would also like to assess people's views on how to use it. I like to think of it as a caster/ melee class which is only mediocre at each of these tasks, but really shines with special abilities (gaze attack, Shadow Chains). With that in mind, here are my thoughts:
1) Grasping Darkness is interesting in that it allows you to attempt a grapple after a successful touch attack, the range of which increases as you take levels in the class. Since you're taking the Evangelist archetype and it's already been suggested to increase charisma, why not try Eldritch Heritage: Aberrant for the usual reason? You get to increase your melee touch range even more! The flavor seems solid: Zon-Kuthon is all about beauty in malformation--you could even spin it as a limb-extending body modification. At character level seventeen, when you conveniently attain your final level of Umbral (Court) Agent, your shadow chain reach increases to twenty feet and your touch attack augmentation from Aberrant increases to fifteen. The language all seems to comport with the view that you would be able to use shadow chains at a range of thirty-five feet and initiate grapple attempts! Between moonlight stalker and the +5 to the grapple check for being in darkness, you would stand a good chance of succeeding on a grapple from a huge distance.
2) On that subject, why not get a bit better at grappling? You could enter the class with only three levels of cleric. Tetori 4 is a nice break point, as you get good bonus feats, no hit to your BAB for the purposes of CMB, and amnesty from most of the normal grappling penalties (although you don't gain the grappled condition with Grasping Darkness, so that doesn't matter much). Monk (Tetori) 4/ Cleric 3 still allows earliest entry.
Most monk archetypes could work, actually; you will miss out on free Stunning Pin, but nothing is stopping you from taking it as a normal feat once you have Improved Grapple and IUS from your monk bonus feats. Monk three for maneuver mastery gives you four levels of a casting class. I agree that cleric is best (probably better than Inquisitor or Sorcerer (Empyreal), which are the other wisdom-based casters I have considered for this prestige class), although, given that Zon-Kuthon has a druidic sect dedicated to him, I wish the class didn't require a lawful evil alignment.
The monk levels drastically reduce casting ability, so I understand if this route looks unappealing.
3) A last point: I considered ways (Conductive weapon property, Domain Strike feat) to try to attach Shadow Chains as a rider to other attacks. My idea was something like this: get a conductive spiked chain, smack someone with it, then conduct Shadow Chains through and grapple a more distant opponent, imagining that you've put your spiked chain right through an opponent and are projecting your shadow chain through him/ her. However, the language for all such abilities seems to indicate that the conducted ability affects the opponent struck, so no dice. I just wanted to throw that out there in case anyone can make it work.
I hope something here appeals to you. Let us know what is decided on!