1. if you want a new handle, take the old handle to the store and buy a
new one like it. the nut probably is a left handed thread. be careful
to measure the handle's hole size and shape. take a picture.
2. no, take the old gasket to the store and buy one the same size.
their sizes do vary. no rocking is permitted it will cause a water
supply leak in the future.
3. wrong, no leaking whatsoever is permitted. no goop or gel is needed.
4. re-d the directions. we use fluidmaster parts on twenty toilets but
some tank-to-bowl gaskets vary.
wax gaskets vary due to floor flanges altitude related to floor
altitude.

if the commode bowl on the floor rocks your plastic horn wax seal may
need to be replaced with a plain wax seal that fits.

see also www.fluidmaster.com
for excellent free website support.