This is very weird. I've got all the answers (pretty sure they are all correct) and if I'm right then 16d can only be one thing - (3,3,2) - but if I've interpreted the instructions correctly then I can't get the letters to make the phrase.
I've removed letters for 6 answers and added letters for 5. But there are letters in the phrase that are not in the list of the letters I've added and there are letters in my 'removed' list that are not in my 'added' list so they can't be 'offset!'
Just to check:
Does "Offsetting letters removed against ones added gives a surplus of eight added letters" mean "for each removed letter" delete it from the "added letter list"?