It's possible to get 0% unemployment! I actually had -2% for a while (less than a month) until the capital strike struck.
I would suggest that you change the code so that if the unemployment gets bellow 0.1 it's set to 0.09 to avoid this (not via event as you could get more unemployment in another event and then click the set unemployment to 0.09% event), and to ad a line at the end in case you have less than 0.1 unemployment, maybe something like "Unemployment has sunken to a level where they are insignificant! This is a success of our economic policy."
The game can clearly still be beaten, I could have done better electorally if I had not insisted on passing all three land reforms, taking the State Buyer decision and passing every social reform as I had to defund the unemployed and such...
To do this you have to pass WTB-plan twice, (the second one HAS to be after 1930 has begun) and expand the councils three times before you pass three(!) nationalizations and then get the capital strike and empower workers to seize the factories without raising taxes ones. (Done on easy)