Exodus 19
3 And Moses went up unto God, and the Lord called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel;
4 Ye have seen what I did unto the Egyptians, and how I bare you on eagles' wings, and brought you unto myself.
5 Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine:
6 And ye shall be unto me a kingdom of priests, and an holy nation. These are the words which thou shalt speak unto the children of Israel.
As I was trying to tell you, for much of the OT days ever since Mount Sinai, you first had to be part of Israel, and you have to obey the Law of Moses to, as you said, "diligently seek him".
Don't get me wrong, I am as happy as you now that we have Romans 3:21 and Romans 4:5 to show our faith in God, apart from works.
But that does not mean those in the OT could rely on that too. But if you insist they could, alright then, we can agree to disagree.