Other options in the main and in the board were
Engineered explosives
Su quata firewalker
Wasteland
Crucible of worlds
Pernicious deed
Suq'Ata Firewalker is bad because it costs double-blue, and you will have trouble keeping Mana Drain (or Counterspell) mana open in the early turns if you play him to deal with a Welder or a Grim Lavamancer or whatever. Better to rely on Firestorm for killing dudes.
Wasteland is bad because you have trouble fixing your mana anyway and cannot fit any colorless lands into your mana base besides
possibly Library of Alexandria. Bringing in Strip effects is tangential at best to your strategy and would cause lots of color problems.
Crucible of Worlds is bad because you shouldn't need it to beat opposing Crucibles--that's what Artifact Mutation and all the basic lands you should be running are for--and you don't have Wastelands of your own to recur.
Pernicious Deed I guess is for help against Fish? With 3 Old Man of the Sea and a Firestorm, is Fish really so big a threat (both as a matchup and in terms of expected numbers) as to deserve additional dedicated slots? I doubt it.
Engineered Explosives is the one choice I could see actually considering. You should be able to set it off for three, killing several important drops for Stax decks, fairly reliably, and setting it off for 1 or 0 could be good in certain matchups, particularly combo. Unfortunately, it is pretty solidly a sideboard card and I don't see what it is really better than. Possibly the Ground Seals, but is an autoloss against Dragon really acceptable, given how easy it is to protect against? Possibly cut your maindeck Crucible and move the Fact or Fiction there, then add a Gaea's Blessing to beat Dragon and cut the Ground Seals for Engineered Explosives, which are better against Welder decks, anyway.
The one matchup that still worries me is Oath. Isn't "Orchard, Mox, Oath of Druids" a "Force of Will or no?" sort of scenario for this deck? I guess you could go for broke and try to race, but Akroma and Spirit of the Night are quite reliable and you'd need to draw pretty well to muster 20 by turn 3, particularly given that Akroma can stop 6 of it and live. I'd like to hear some sb options for that matchup.