I'll try to be there  Been hoping to see some vintage in CO!

From the Stigma Lasher part of the Eventide FAQ:
-- Spells and abilities that would normally cause that player to gain life still resolve, but the life-gain part simply has no effect.

So yes you can.

From the Gatherer:
4/1/2008     The last ability counters all spells on the stack with any of the appropriate names, no matter who controls them.

So it's just ones that are on the stack right then that are countered.

4/1/2008     The only cards you turn face up are the cards exiled with the Grimoire Thief that was sacrificed.

Thus they go in separate piles if you have two, and you can't reveal all by sacrificing just one.

Have the blood moons/magus of the moons worked for you without any basic lands? It seems like they would hurt you a fair amount since they cut off 12 cards. Maybe switching some of them to the sideboard would be better.

With blue already, ancestral and time walk are excellent of course and should be run. This also works well with moving some of the moon effects to the board.

Taking out the torch and channel sounds good. Has wheel of fortune worked well for you? It can tend to help your opponent as much as you. It could be worth taking out or moving to the sideboard.

Greater Gargadon is always a possibility against oath that would probably work well.

I assume you don't have on color moxen or lotus? If you do, run them of course.

I would take out an overgrown tomb and add another fetchland of some sort. I must be missing how you cast banefire; where do you get the red mana?

Demonic tutor seems very useful since you're already running black, and it can find a combo piece.

I'd try to find room to run some artifact (or artifact/enchantment) destruction. Damping matrix, although it isn't often played, completely hoses your deck. And chalice on 1, while not instantly fatal, is another big problem, and there are probably others. Plus it makes demonic tutor more useful and helps against key+vault.

As far as I can tell there's no kill mechanism there yet is there? I think cunning wish is standard, and stroke of genius + braingeyser in the sideboard. I don't have much experience but 3 cunning wishes seems decent.

Spell pierce seems more versatile than disrupt. It can catch artifacts and the occasional rogue enchantment, and is harder for someone to get around by paying the mana. Have you tested it?

How about lotus petal? Since you don't have any moxen/lotus available it should be good helpful.

That leaves 3 slots. If you're getting crushed by wastelands and/or blood moon a basic swamp would be good.  If you do add a basic swamp, switch the scalding tarns for fetchlands that can find swamps of course. If you have trouble with leyline or other graveyard disruption, another chain of vapor or echoing truth would be good. If you have trouble with key spells getting countered, spell pierces are useful.

I would put another chain of vapor in the sideboard to wish for. If you're running into people with power, null rods would be good too. 

In my experience, the spellbombs are poor unless you are somehow making use of their artifactness. In that case they're just mediocre. You wouldn't be using them as artifacts, in fact they would be bad as artifacts because of null rod. The only thing the spellbomb would seem good for is Iona for blue. Although I don't have any suggestions there, I don't think Aether is worth it. If you want to bounce big creatures go with echoing truth.

Without any ways to shuffle your library (correct me if I missed one), ponder might be better than brainstorm. Ancestral certainly would be.

Time walk seems like it would be really good in your deck, so I'd say yes. Although there might be a better choice to take out, someone else probably has a better idea for it than I.

Edit: Time walk, not Time, lol

It seems to me explore should be compared with exploration. So-

Explore:
-cantrips

Exploration:
-costs one less
-sticks around

You suggested crucible with strip in shops. Exploration would certainly be better there since you get to keep recurring the strip mine. In relation to playing an extra workshop, explore could conceivably be better since it cantrips, but then again, exploration could be better since it is cheaper. Tellingly however, exploration isn't played as far as I know. Even assuming explore is better in shops, it doesn't seem like it would be that much better.

In fish, tempo is already lost a bit since explore costs  (or worse  ). If you want to play a one drop, it seems like it would be better to play a one drop and then serum visions or something similar. I don't know enough about fish yet to say definitively that explore is bad, but I certainly don't have high hopes for it in fish either.

In general, it could have a place in vintage that no one has thought about, but in my opinion it probably doesn't.