Maelstrom Wanderer and Melek's Force of Will

[LotusHead]

Maelstrom Wanderer:
Creatures you control have haste.
Cascade, cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order. Then do it again.)

Melek, Izzet Paragon
Play with the top card of your library revealed.
You may cast the top card of your library if it's an instant or sorcery card.
Whenever you cast an instant or sorcery spell from your library, copy it. You may choose new targets for the copy.

We're playing EDH, and I have been going broken with my Melek. I'm tapped out, but there is a Force of Will on top of my deck.

My opponent baits a few spells, then casts his Maelstrom Wanderer from the Command Zone.

I assume that what happens is now this: His Melstrom Wanderer goes on the Stack, then 2 castcade triggers go on the stack.

So...
top
cascade trigger
cascade trigger
Maelstrom Wanderer
Bottom.

I wist to counter his Wanderer and whatever he flips for the top cascade trigger (and let him resolves the 2nd cascade spell that's in the middle).

Opponent thinks that I can't counter the Maelstrom Wanderer until both Cascade triggers resolve. he flips rite or replications first (which I would LOVE to counter, as his only target would be my general) and some Garruk planeswalker).  It was casual MWS play, so that stuff kinda happened before our rules disagreements dominated the rest of the game.

I am quite sure that I can counter his Maelstrom Wanderer and his Rites and let whatever 2nd cascade (Garruk) resolve as Maelstrom Rites and Cascade 2 was all on stack.  Did I miss something here?  Opponent thought I didn't have the option of putting "force your general" on the stack.

Am I missing something here?

Thanks for help (I wouldn't play a game 3 if we didn't agree on how cascade works, as that is is game plan, but he was certainly friendly and tried his best to talk it out)

[AmbivalentDuck]

Yes. You can't counter Rite after Garruk is revealed. Cascade triggers happen one at a time.

[LotusHead]

So can I counter his Rites and Maelstrom Wanderer?

[AmbivalentDuck]

No. After he flips Garruk, Rites has already resolved.

1. Cast Wanderer, two triggers are on the stack above it.
2. First trigger resolves, Rites is on the stack with a trigger and Wanderer below it.
3. Rites resolves, trigger and Wanderer on the stack.
4. Garruk goes on the stack with Wanderer below it.
5. Garruk resolves.
6. Wanderer resolves.

From the moment you've seen Garruk, it's too late to touch Rites.

[ed0]

I don't think that was what he was asking, AmbivalentDuck.

Once the first cascade trigger resolves and Rite goes on the stack (your step 2) he can respond with a counter from the top of his deck targeting the rite and with the copy from Melek targeting the Wanderer.
Assuming no responses from the opponent the two counters resolve.
The stack then looks like this: Rite (countered), trigger, Wanderer (countered)
The trigger resolves putting Garruk on the stack.
Garruk resolves.

His opponent seems to be somehow under the impression that the triggers on the stack somehow protect the Wanderer from being targeted or countered.

[LotusHead]

Thank you all for the responses. I think I got what I need here.