DedWards

You seem to be going for a tap / untap theme here to reuse the spells on Kaho, Minamo Historian and Elite Arcanist. (explaining this in the Deck Description would be nice). Two cards I suggest you look at including are Freed from the Real and Triton Tactics. (also, Evolving Wilds / Terramorphic Expanse will help with the mana)

Training Grounds

Interesting build. Maybe Dryad Militant for sideboard? If you make one, that is.

Sorry, forgot it can target Artifacts too.

I've played against the Orb many times, and it works. Remember, the opponent is the first to suffer from the effeffect of the Orb AND you're milling with many other effects.

Apostle's Blessing looks like a waste of space, you only have 1 creature.

Mesmeric Orb might help.

I know Oppressive Rays costs 1 mana, but they can eventually afford to pay to attack with it. Temporal Isolation has flash and might be a better fit as a surprise.

Khalni Heart Expedition is an awesome card, just wish I had more of it.
Have you thought about using Recross the Paths?
Vigor is a big creature that would fit nicely in here.

Ghoulcaller's Bell might be better than Shriekhorn. While Ghoulcaller's Bell might mill for less per activation (only 1 per activation), Shriekhorn is limited to how many times you can activate it (it only has 3 charge counters, thus 3 uses).

You may want to consider Jace's Erasure and Curse of the Bloody Tome as passive mill. Jace's Erasure works nicely with Thought Scour and Pilfered Plans.

If you can get your hands on some, Counterspell is better than Mana Leak. Counterspell was printed as a common in 5th Edition, thus it's legal in Pauper.

Only one person plays Splinter Twin and I've added Batwing Brume to my sideboard for that :p

As the Shinobi have trigger effects for dealing combat damage to an opponent, I think cards like Sleep could be pretty cool mid to late game.

Looking at your creatures I'm noticing that they tend to have a higher toughness than power. Two cards that mill because of this that may interest you:
Doorkeeper - requires you to run more creatures with defender because it mills equal to the number of creatures you control with defender.
Phenax, God of Deception - grants your creatures the ability to mill equal to their toughness and doesn't care about defender.

Lol, that Increasing Savagery combo is funny.

Besides it's price tag, Bitterblossom makes black tokens, thus not getting a buff from Honor of the Pure.
A friend has a Sorin, Solemn Visitor I've been trying to get, but no luck yet.
Lucky for me, no one in my group is playing affinity nor Tron, but I'll consider it if they start playing them.

Evolving Wilds thins out the number of lands in the deck, increasing the chance to draw much needed nonlands.

Extra unneeded cards make for perfect discard options for Faithless Looting, Tormenting Voice, and Wild Guess, allowing me to hold onto better cards. Remember, I'm trying to make this mono red, if I where to add blue like most storm decks, I'd include a whole range of other, potentially better cards.

Thins out the number of lands in the deck, increasing the chance to draw much needed nonlands.

Past in Flames is a good card, but it costs $4.89 a pop where Pyromancer's Swath only costs $0.59 and allows for a much lower storm count.

Boggart Ram-Gang - 3 mana 3/3 GR hybrid creature with Haste and Wither.

Kiora's Follower might be a better fit than Voyaging Satyr as it can untap any permanent. This allows you to untap the enchanted land like Voyaging Satyr is in here for, but also gives you a pseudo vigilance granter for the bigger creatures later in the game.

There's a flaw to your plan: Tentacruel's extra turn ability only happens if you CAST it.
This means that Tentacruel entering in any other way will not grant an extra turn, including coming back from the closet closet's effect.

Also, Tentacruel may be colourless, but that doesn't make it an artifact. (Just in case you thought Darksteel Forge gave it Indestructible)

Spirit Link, Vampiric Link and Spirit Loop all gain life equal to the damage the enchanted creature deals, but unlike enchantment that grant lifelink, the life gain ability of these three are cumulative. In Spirit Link's and Vampiric Link's case, you can even put them on an opponent's creature and you will gain the life, not the opponent, effectively nullifying the damage it can do to you.