Fuel/back end

I have a 2005 Crown Vic P71. I have noticed that
the back end feels off and today  lost  a lot of gas
in under a mile. The car filled up with the smell of
gas and every time I stopped and then got back on
the gas it gave the sensation that my tires were
spinning but they wasn't. Once I got to where I was
going I could see the fuel leak trailer. Could this be
a fuel line? Now. Before all this happened I could
smell gas around and in the car every once in a
while. The second thing is. With the back end
issues...I noticed that when I would slow down to
stop (not fully stop) and get back on the gas my
car would act as if was in between gears. What
causes this? I'm not ready to fully retire her just yet