1)
What is "Tzerufah"?
1.
Radak, Malbim: It is without any impurities. Mesilas Yesharim (Perek 16) - true Avodah must be purified much more than silver and gold.
2)
Why does it say "v'Avdecha Ahevah"?
1.
Radak: I [love Your words, and] remember them always, and they forgot them.
2.
Malbim: Nothing stops me from guarding Your words. They themselves do not stop me - they are Tzerufah, without any impurities. And there is no impediment due to me - I cling to them with love, not amidst hope for reward.
