I suggest getting a proper 46 mm or 1 13/16" socket ($19 from Sears or $10
from Tractor Supply), a breaker bar and a 4" long 2" pipe.  A 200 lb man
can gently exert 800 lb ft of torque by standing on the pipe and much more
if he bounces a little.  If a LARGE chock is used the van will remain in
place.  An additional chock placed at the alternate wheel will also help.

The proper socket will not slip off the nut nearly as easily as the flat
plate hammer wrench.  You will also not chance destroying a lug or hitting
the wheel with the hammer.  You will be able to properly torque the nut
when you are finished by gently standing on the pipe at the proper place
determined by dividing 365 lb ft by your weight (in pounds).  No bouncing
this time.

I've done this many times.

Don't hit the striking face of a hammer with another hammer.  Both are
hardened steel that has been made even more brittle by work hardening.
They can shatter violently.  Always wear safety glasses!