But how much did "the God of the Old Testament" love mankind?
Enough to walk among His creation, at the very least. Listen to what He told the Israelites:
12 "I will walk among you
and be your God,
and you will be My people.
13 I am Yahweh your God..." Leviticus 26
YHWH, the Almighty God, has no problems entering into His creation. And why would He, when He created it to be good? (Genesis 1)
Did you know that:
✦ YHWH literally walked the earth and walked and talked with Adam and Eve, fellowshipping with them and enjoying their company (Genesis 3)
✦ YHWH physically appeared to a very distressed Hagar, mother of Ishmael, in Person, in a visible Form:
"Thereafter, Hagar used another name to refer to the Lord, who had spoken to her. She said, “You are the God who sees me.” She also said, “Have I truly seen the One who sees me?” (Gen 16:13)
✦ YHWH physically came down to earth to visit with man (Gen 18, Gen 31, 32, Judges 13). Not only that but YHWH comes to earth as a human being Who eats what Abraham serves Him on earth (Gen 18)
✦ YHWH physically wrestled with Jacob (Gen 32)
✦ YHWH physically appeared to Moses in a burning bush (Exodus 3)
✦ YHWH appeared to Moses, Aaron, Nadab, and Abihu, and 70 of Israel’s elders,
"... they saw the God of Israel. Beneath His feet was something like a pavement made of sapphire stone, as clear as the sky itself. God did not harm the Israelite nobles; they saw Him, and they ate and drank." Exodus 24:9-11
And that is Who some call "the God of the Old Testament," the God of Abraham, Isaac and Jacob: He walks among His people, He talks to them, wrestles with them (they always lose, of course), He comforts them, guides them, and shelters them. Lo and behold, He even dines with them.
Sounds an awful lot like the Jesus of the New Testament, Who had this to say to those who think they can get along fine without Him:
"Listen! I stand at the door and knock. If anyone hears My voice and opens the door, I will come in to him and have dinner with him, and he with Me." Revelation 3:20
The Bible is clear that we don't have "different Gods" in the Old and New Testament.
We have One God.
The loving, nurturing, caring and compassionate God of the Old Testament is the very same loving, nurturing, caring and compassionate God of the New Testament.
If you don't yet have a relationship with that God today, ask Him with all of your heart to reveal Himself to you and start reading the Bible. He will answer your prayer the same way He's been doing it for thousands of years:
with His life-changing power!