SH,
Perhaps this is enough to get you there, given that you have the answers.
2: wordplay gives 3+1+2
11: &lit, with wordplay giving 3 around 1+3
16: wordplay gives (3+3) rev
28: wordplay gives 2+3
29: wordplay gives 5, with 1 exchanged for 3
For 20, I think that there is enough of a link for the definition to work. See #33 of the definition and #7 of the answer.