Pure good is a poor reason to argue UMD imo. Sure it hits almost everything, but it's only 1d6. Fire shield scrolls, OTOH, are solid gold.

I question the use of Extend Spell. Perhaps it'll be useful early on when your caster level is low, but at level 20 the only things you'll notice it affecting are divine power and divine favor. No one needs a 40-minute deathward. My suggestion would be swapping it out for Empower Spell once you're in the 11+ levels.

I'll also question the Prayer of Incredible Life enhancement. You need the first tier for RS, but you'll find that most of the time a crit heal is overkill even without II and III. When you start using divine punishment, a few tiers of Cleric Smiting will make a bigger difference. Improved Empower Heal is also underwhelming.

Mental Toughness vs Spell Penetration I'd put as a personal choice. If you stick to damaging spells or don't cc enemies with SR, spell pen is a nonissue. It's also a nonissue until the Vale or later. Mental toughness is still not a very good feat, but there's not many other options. I personally like your choice of Extra Turns, but my cleric does more healing via radiant burst than anything else.