Python 2, 340 - 8 = 332

s,o=raw_input(),''
for z in s:
 if z in'Hh':o+='Hello World!'
 elif z in'Qq':o+=s
 elif'9'==z:
  i=298
  while~-i:print i/3or 99,'bottle'+'s of beer on the wall.\n'[2<i<6:9+i%3*12]+'..\nGToa kteo  otnhee  dsotwonr,e ,p absusy  isto maer omuonrde,,'[(i>3)+i%3*68::2];i-=1
 elif'+'!=z:o='Source code contains invalid characters';break
print o

s,o=raw_input(),''
for z in s:
 if z in'Hh':o+='Hello World!'
 elif z in'Qq':o+=s
 elif'9'==z:
  i=298
  while~-i:print i/3or 99,'bottle'+'s of beer on the wall.\n'[2<i<6:9+i%3*12]+'..\nGToa kteo  otnhee  dsotwonr,e ,p absusy  isto maer omuonrde,,'[(i>3)+i%3*68::2];i-=1
 elif'+'!=z:o='Source code contains invalid characters';break
print o

Python 2, 345 344340 - 8 = 337 336332

s,o=raw_input(),''
for z in s:
 if z in'Hh':o+='Hello World!'
 elif z in'Qq':o+=s
 elif'9'==z:
  i=298
  while~-i:print i/3or 99,'bottle'+'s of beer on the wall.\n\n'[2<i<6\n'[2<i<6:9+i%3*12]+'..\n\nGToa\nGToa kteo  otnhee  dsotwonr,e ,p absusy  isto maer omuonrde,,'[(i>3)+i%3*68::2];i-=1
 elif'+'!=z:o='Source code contains invalid characters';break
print o

Python 2, 345345 344 - 8 = 337337 336

s,o=raw_input(),''
for z in s:
 if z in'Hh':o+='Hello World!'
 elif z in'Qq':o+=s
 elif'9'==z:
  i=298
  while~-i:print i/3or 99,'bottle'+'s of beer on the wall.\n\n'[2<i<6:9+i%3*12]+'..\n\nGToa kteo  otnhee  dsotwonr,e ,p absusy  isto maer omuonrde,,'[(i>3)+i%3*68::2],;i2];i-=1
 elif'+'!=z:o='Source code contains invalid characters';break
print o