"I came to throw fire on the earth" or "I came to set the earth on fire." Possible meanings for this metaphor are 1) judgment or 2) purification or 3) division.
This is an exclamation emphasizing how much he wants this to happen. It can be translated as "I wish very much that it was already lit" or more generally as "How I wish that it had already begun." (See the section on Sentence Types in [[rc://en/ta/man/translate/figs-sentences]].)
Baptism is used here as a metaphor for suffering. Just as water covers a person during baptism, suffering will overwhelm Jesus. This can be translated as "I will be baptized with suffering" or as a simile: "I must be overwhelmed in suffering as a person being baptized is covered by water." (See: [[rc://en/ta/man/translate/figs-metaphor]], [[rc://en/ta/man/translate/figs-simile]])
This exclamation emphasizes how distressed he was. It can be translated as “I am terribly distressed and will be so until this suffering is completed!” (See the section on Sentence Types in [[rc://en/ta/man/translate/figs-sentences]])