There is one more step of the quest available! You have to talk to a guy, that is standing right where the guy was who was selling pokemon in 7th street stupid english...
Then try that, after 3 calm minds my lvl72, 252 EV spa, 26 IV spa, calm nature Alakazam did not manage to one hit garchomp and then got ko-d by it. With one calm mind you wont even get past excadrill.
To do that he will need a good EV trained alakazam with good IVs and atleast lvl 72-74. He will also need at least 4 calm minds. It is doable but a little hard.
I would replace scrafty and alakazam with azumarill and something that has a grass attack (for quagsire), ampharos too for maybe a kingdra. Also level them all up to at least lvl70, I would go till 73-4. Why doesn't your blaziken have high jump kick?
It is the house right under the Beryl Ward entrance. If you have checked there already, it could be possible that you have done the event while it was the Azurill event. If everything else fails check in rpgmaker under Jasper Ward > Jasper Shack its there.