I know this sounds counter intuitive but seeing as it has moved slightly give it a sharp twist anti-clockwise (tightening) then remove as normal, used to do this in the bike shop worked more often than not
Besides "the usual [so far unsuccessful for you] technique for removing a freewheel from its hub - to clamp the freewheel puller into a solidly-mounted vise (sic) and unscrew the wheel from the freewheel" he suggests:
"An alternate approach . . . for really obstinate freewheels: to use a suitable box wrench to hold the tool, and strike the wrench handle sharply with a big rubber mallet."
Soak the whole thing in white Vinegar for 3-4 days then give it a go.
If not
Then I would stick it in a vice & introduce heat (cutting torch) to the freewheel body as all cogs should be removed along with pawls & bearings. Its a last resort but it will work.
My thoughts exactly.It is very easy to get the orientation wrong when you are turning a wheel over to remove the wheel from the block and not the other way around.
Peter