So far the dragon appears to be happy to remain perched on its horde next to the large bottomless cavern inside the main volcano shaft. We've poked it a few times to test its responses, mainly to see if we could use a decoy or summoned creatures to lure it away from the horde while we go in and steal it. As far as I can see, the dragon doesn't have any method available to magically seal the fissure we're using, nor does it have any shapechanging magic to chase us down our 5 ft. by 5 ft. rat-hole. It could always drop a boulder on the entrance, but pushing it back out of the way shouldn't be too hard for our melee characters (it's not like they're contributing much else to the fight anyhow).
As for going toe to toe with a fully awake and angry adult red dragon, my Wizard's pretty well equipped to handle it. Obviously Resist Energy and Protection from Energy to negate the breath weapon, Blur and Mirror Image to avoid too many melee hits, and lots of teleportation SLAs from my Conjuration school specialization to get the hell away if I take too many hits. I have 100 hit points, so I should be fine even if I take a big hit with a Greater Vital Strike Power Attack. I'm just hoping it doesn't ready Dispel Magic to counterspell my Enervations, since that's the biggest risk to the strategy. I'm considering whether to summon a half dozen lantern archons to zap it with lasers while I tag it with enervations as a distraction too, just to add a little extra chaos.