Why does it say "Lachen Chai Ani"?
Malbim: He sealed the decree with a Shevu'ah.
What is the meaning of "l'Dam E'escha"?
Rashi: You will fall to the sword.
Radak: I will fix and prepare you for [falling to] the sword.
Malbim: Just like you spilled blood, you will be full of blood of people killed.
Did they hate blood?
Rashi #1: You disgraced the Bechorah ? My Avodah was for the Bechoros, and you hated to dirty yourself in blood of Korbanos of My Avodah ? therefore blood of the killed will pursue you.
Rashi #2: You fear murderers, like everyone does, and murderers will pursue you.
Rashi #3: You hated your brother, who is your flesh and blood.
Radak: You hated people who spill blood.
Malbim: Your hatred was hatred of blood, not due to benefit or fear of damage.
How will blood pursue you?
Refer to 35:6:3:1-2.
Targum Yonasan: People who spill blood will pursue you. Radak - until now you guarded yourself from them; now they will catch you.
Malbim: They will not pursue you to take captives and spoils, only to spill your blood, just like your name is Edom 1 .
Edom is red, like blood. Or, it resembles the word 'Dam'. (PF)