I also love Kiln Fiend and I assume its great in a control heavy metagame. Another interesting guy is "Storm Entity". But as far as I testet, Fiend is the best grow creature.
A few points on your list:
-I really dont think probe is an update. I'd much rather run 4 Duress & 4 Thoughtseize
-Gushdecks almost need 4 Preordains. I'd never cut them.
-My Fiend.deck is currently running 2 Lightning Bolts MD and 1 SB. I think I need them, especially if confidant sees alot of play. Fire/Ice may be good but I want to be able to kill Jace's and Lodestone / Precursor Golems.
I like the deck but I still have serious problems with MUD's. It's just the worst matchup if you play Gushdecks. Controllists with fewer basics and confidant's have alot easier games against our metalfriends

About your Sideboard:
-IMHO shattering spree and ancient grudge are far supperior to steel sabotage. Especially in a list, which wants a high spellcount!
Nice to see other people who like the Grow a Fiend idea.
Best,
Doggue