1) Some people hope that an increase in the number of policemen on the streets will aim at / will lead to (?) a decline in the crime rate.
2) I was so worried that I should be / would be (?) missing / so worried to miss telephone calls that I had a private line and a business line installed in my office, as well as answerphones on both lines !
3) She is French by birth, but she is married to an Israeli and (has?) taken Israeli nationality.
-->The word "has" is correct there. However, it might be better to say "Israeli citizenship" rather than "Israeli nationality".