You are very correct. There is no Church dogma or other canon law that says it is a sin to vote for a candidate that is in support of choice. (I won’t say supports abortion because I know plenty of people on both sides of this issue and not one is in favor of abortion.) The Vatican made it very clear in 2004 when Kerry was running that it was up to the individual voter to make their own moral judgement that they can live with. Additionally, the Church also made it clear, again, that you only commit a mortal sin if you directly assist someone in getting an abortion or if you yourself have an abortion.
Not quite. See #131.