When his face melts it's him at his darkest moment. It comes right after he goes on his trip or his "high" shown by the floating of the chair. But then after comes the crashing down. Coming off the drug with horrible withdrawals that tear away his existence (his face). That's also backed up by the jittery way he shakes his arm around like a junkie needing a fix.
I think the box was definetly the addiction he's tried to battle, as he seems to have put it away before in that dark hole beneath his house. Unfortunately he goes back for more but ultimately there is no more. And the guy beneath the floor behind all the gadgets is the provider/dealer that is reeling him in for more.