1)
How is this connected to the previous verse?
1.
Radak: Just like Your word persists in Shamayim va'Aretz, so Your word and promise last with m.
2)
If he did not delight in Torah, would he have perished?
1.
Radak: Yes, amidst grief of my heart.
2.
Malbim: (a) They wanted to stop me from marrying into Kahal Yisrael. Since I delight in Your Torah, I answered them according to Torah law. (b) The merit of Torah protected over me - "Yevo'uni Rachamecha v'Echyeh Ki Sorasecha Sha'ashu'ai" (77).