Muktol

[[Sarevok, Deathbringer]], enchanted with [[Raised by Giants]] and equipped with [[Colossus Hammer]]?

I didn't look at the whole deck but while reading your description I thought of the myriad keyword, added to commander a few cycles ago. What about [[Giant Adephage]], equipped with [[Blade of Selves]]?
Another card I just stumbled upon would be [[Crash of Rhino Beetles]]

I removed [[Thermo-Alchemist]] in all my (pauper) decks and added [[Kessig Flamebreather]] instead.
The "jump start" keyword could also be worth a look: [[Direct Current]], [[Risk Factor]], [[Maximize Velocity]]

[[Karn's Bastion]] and [[Ichormoon Gauntlet]] might be a little to expensive, depending on your budget. Another interesting card for decks that work with a lot of +1/+1 counters would be [[Contagion Clasp]].

I would at least remove [[Pacifism]] for [[Planar Disruption]]. You could also do a split between [[Planar Disruption]] and a removal like [[Cast Down]], [[Go for the Throat]], [[Fateful Absence]] or [[Hero's Downfall]].

[[Nettle Sentinel]]
[[Tribute to the World Tree]]/ [[Elemental Bond]]

[[Disciple of Griselbrand]] or [[Dockside Chef]] could be useful as additional sacrifice-sources. The budget would also allow for some [[Bastion of Remembrance]].

Proliferate, one of my all-time favourites.
A general suggestion would be [[Karn's Bastion]] because a land that let's you proliferate is always a good choice in such a deck. [[Hickory Woodlot]] or [[Saprazzan Skerry]] could help you to speed up your play a little bit.
One of my first proliferate decks used [[Nissa, Who Shakes the World]]. It was always a funny moment when an opponent tried to deal with Nissa and you simply proliferated back what he had done as damage. And running over an opponents defence with indestructible lands is also very satisfying. After this I moved to pauper decks, but they still have some very interesting cards. [[Duskshell Crawler]] is a solid, bolt proof, creature that gives all your creatures with a +1/+1 counter trample. [[Servant of the Scale]] allows you to transfer it's +1/+1 counters on another creature when t dies, making you less vulnerable for removal. If you want some protection for your creatures take a look at [[Snakeskin Vei]]. With 1-2 copies of [[Prologue to Phyresis]] you could turn this deck from beatdown into infect.

[[Invigorate]] is banned in pauper:
https://magic.wizards.com/en/banned-restricted-list

[[Volcanic Fallout]] or [[Respite]]. The 2 damage from [[Volcanic Fallout]] doesn't seem to do much in commander and you have enough mass-removal in the deck and thus the board should be pretty empty, so [[Respite]] will prevent some damage, but the life-gain will be rather low.
You could also think about adding [[Strionic Resonator]], which would double the damage dealt by [[Ruric Thar, the Unbowed]].
Just be aware that the damage dealt by [[Ruric Thar, the Unbowed]]'s ability doesn't count as commander damage. because it's no combat damage.

[[Ruric Thar, the Unbowed]] + Lifelink?
[[Basilisk Collar]], [[Batterbone]], [[Batterskull]], [[Loxodon Warhammer]], [[Shadowspear]]

I've tried a similar strategy, using enchantments to keep an opponent from getting the right mana he would need. But it's like HokieCodeMonkey points out: You cannot stop an opponent from getting at least one right mana if he plays a land in his turn, and this might be enough to put some threats on the field.
The enchantments tough are good for "destroying" dual-lands. You could use [[Convincing Mirage]] if you don't want to have a dead card in your hand on game one, if you run into a deck that uses blue mana.
My own deck uses black as additional colour, thus giving me access to things like [[Mana Skimmer]] and [[Thorn of the Black Rose]] (And yes, it's a pauper deck).

[[Evolution Sage]] and [[Karn's Bastion]] could be an idea.

[[Stonehorn Dignitary]] is a classic target for flicker-effects in pauper.

What about some of the Phoenix-creatures? [[Chandra's Phoenix]] or [[Flamewake Phoenix]] could help against "sudden surprises".

[[Valiant Veteran]]
A description would be a nice addition to your decks. This makes it easier on making suggestions and understanding the deck.

[[Blade of Selves]] could be an idea, tough the tokens won't deal commander damage. Another thing that I like to add to a deck when I'm using a commander that I want protected would be [[Swiftfoot Boots]]. [[Darksteel Plate]] could also be used, but is rather expensive, [[Kaldra Compleat]] or [[Indestructibility]] would be a little bit cheaper.

[[Mirror Box]]/ [[Mirror Gallery]]/ [[Sakashima of a Thousand Faces]] would enable you to generate a large number of 3/3 Frogs and slowly drain your opponents of their life.

I added 2 [[Pentad Prism]] instead of 2 basic lands. There where some occasions where I would have been able to cast another proliferate spell with just a little bit more mana, or proliferate and activate [[Festercreep]], tough those situations where rather rare.

I don't have an auto-correction, I'm writing things on a computer in a browser... which checks for spelling, but doesn't change it automatically. These are simple mistakes I didn't see at the time I was writing it.
But yes, auto-correction can be a bitch. The word, or in this case the acronym, I'm having the most problem with would be "DSA" which is always converted into "DAS" (German spelling rules).

[[Sphinx's Tutelage]] could convert the deck from a beatdown to a mill strategy. Big surprise for an opponent on Game 2.