1)
What curse did he love?
1.
Rashi: The curse of Hashem - he denied Him.
2.
Radak: David loved the one who cursed him, he was not concerned for the curse.
3.
Malbim: It is the curse that he gave in Dinei Shamayim.
2)
Why does it say "va'Tevo'ehu"?
1.
Radak: It will come; past tense used in place of future. This is common in Tanach, especially in Nevu'ah.
2.
Malbim: The curse will come on him (the one who cursed).
3)
What Brachah did he not desire?
1.
Radak: I (David) would bless him if he would do good to me.
2.
Malbim: I will get a Brachah in place of his curse. He will have no share in it, for he did not want a Brachah; therefore, he is distanced from it.