I am not convinced of the efficacy of enchantments (and you are right, esp. local enchantments). I rather have a one mana instant that does something for me when I need it unexpected by my opponent - and like I said charms rock because they give you a choice, widening their usefulness.
Death Pits of Rath turns (almost) every creature you have into a type of Basilisk. It's cool. Global Enchantments are also the hardest type of card to get rid of (except possibly land).
Ebony Charm? It has three uses, but...
...gain 1 life, opponent loses 1 life doesn't help the poison deck win
...remove 3 cards from graveyard is extremely limited in usefulness
...target creature gains fear is only marginally useful.
As for Tropical Storm - do you think I should switch them to hurricanes?
No. Both don't actually help your deck - they kill the mosquitoes, don't work against non-flyers, and Hurricane, as it deals damage to your opponent, isn't working towards the core theme of your deck. (Hurricane is awesome when you want to deal damage to your opponent. Not so good with poison.
Defense against flyers for a poison deck? Give me a Cockatrice! Or a Royal Assassin.
The version I am playing now has 3 City of Solitudes in it, so I took out the fogs.
I love that card.
Thinking about your deck, I'd try something like this myself:
7 x Forest
8 x Swamp
3 x Bayou
4 x Taiga
4 x Llanowar Elves
3 x Wall of Blossoms
4 x Marsh Viper
4 x Sabertooth Cobra
2 x Cockatrice
1 x Silklash Spider
3 x Elvish Aberration
1 x Sol Ring
2 x Giant Growth
1 x Demonic Tutor
2 x Diabolic Edict
3 x Dark Banishing
2 x Jayemdae Tome
2 x Serpent Generator
4 x Fire Whip
There's a bunch of later cards in there, but it's all from before the cardface changed. It may be one or two lands short, and I'm really not sure of some of the balance...
The Elvish Aberrations have "Forestcycling", which allow you to pay 2 mana and discard them from hand to search for a forest... including the Taiga and Bayou! If you can actually cast them (6 mana), they tap for GGG, which helps fuel the Jayemdae Tomes and Serpent Generators. Normally they'll be cycled, though. The Dark Banishings are terrors that also kill artifacts, and the Wall of Blossoms are cheap cantrip 0/4 walls. One of my favourite cards.
Cheers!