I love mono color decks personally; the consistency and reliability of them is underrated. I think this a sweet build too, my only comments are:

1) I like using Prey Upon in these green stompy decks. Super similar to some of your spells, but also a little cheaper mana cost.

2) A copy of Sylvan Scrying to tutor for Nykthos, Shrine to Nyx probably wouldn't hurt the consistency of the deck.

+1 from me.

Primal Bellow is ok

Utopia Sprawl WITH Arbor Elf

already using it, sometimes we just add Utopia sprawl, even tho it puts the deck at 64 cards, it work's pretty well.

nice deck. I made a similar deck here I would definitely use shapers sanctuary

Bellowing Tanglewurm IS FUNNY

Might of Old Krosa OR Tireless Tracker HELPS WITH CARD DRAW AND GETS BIG

Tajuru Preserver for the sibeboard, maybe? Something to deal with flyers would probably be useful. Plummet comes to mind, though there are lots of other options.

Yes, Tajuru Preserver could be very useful, especially against cards like all is dust. As for flyers, I am using Raking Canopy, so far has worked very well.

I'd drop Reverent Hunter for Strangleroot Geist I would also play 2 Rancor mainboard if you have the budget I would also add 2 Rhonas the Indomitable.

If you like the high curve I would recommend Vorapede and another one drop mana dork

This is the basic stompy list (a competitive mono green agrro deck that uses devotion) might helpFast Stompy (Budget)

Awesome deck!

Have you thought of actually adding a Nylea, God of the Hunt?

I would recommend Rancor, Strangleroot Geist, Avatar of the Resolute as possible additions. They're all cheap. Scavenging Ooze and Dryad Militant would be neat sideboard additions. I have a similar deck to this, but a little more aggro.