As in sign language?
no, as in signature
No, as giving your autograph (=חתימה)
As in putting on a seal
Can't most of these sentences be translated as the immediate future as well? "I won't sign"
Yes, as can the progressive variation in English. That's why we stick to the present.
aní lo chotém, todá.
Sure. The deal is suspect.
The offer is not enough