You are saying Psalm 69:5 does not apply where it speaks of "sins" or "guilt" but then for your purposes use Psalm 69:8. This is simply contradictory. No remarks on one being blind needs to be said when the Psalm you are using is not consistent in what you are trying to say.
"5 O God, thou knowest my foolishness; and my sins (or guilt) are not hid from thee." <---- Doesn't apply, Christ does not sin.
"8 I am become a stranger unto my brethren, and an alien unto my mother's children." <---- Now applies as Christ.
Did Christ take on the sins of humanity or not?
And if that is not Jesus speaking who is it?
It is not David
I did not say it does not apply. Those are Christs words.