Off topic, if the Antwerp merchants had purchased Iceland, would that have brought it under Hapsburg control, or would it have been a different arrangement?
I imagine they'd have tried to run it as a sort of corporate colony, collecting taxes and selling fishing concessions. This would probably piss off the Icelanders enough to revolt, at which point the Antwerpers would request Habsburg help putting it down. This could lead to either a renewed Icelandic Commonwealth (under the protection of Denmark, France, the Hanseatic League, etc.) or to more direct Habsburg rule. It should be noted that at the time, Iceland was still Catholic, and could conceivably remain so without Danish imposition of the Reformation.
In a Henry VIII buys Iceland scenario, it might follow a similar trajectory to Orkney and Shetland. Denmark would try to get it back after the debt clears up a bit, but I don't see any reason for them to be more successful than OTL. The presence of another, larger, Northern Isle might help with the preservation of Norn culture, though there would still be considerable English pressure.