You post sounds like what you see posted by ignorant or antagonistic atheists. I can understand how in isolation we can see a jealous angry God contrasted with God as a loving Father, but that is not how you understand a book which has approx. 800,000 words for a reason.
The parts of the OT in which God can be seen as a jealous angry God are mainly in the context of God having gone to great extraordinary lengths to deliver a people, who were complainers and rebellious by nature, from their bondage .
And for whom God showed Himself to be real, powerful, and intent on making them a great nation and able to do so, And after clearly supernaturally manifesting Himself as Very Real, God offered them and entered into a covenant with them, in which their part was to to keep the commandments given them.
To put it in sports terms, these were a band of misfits who were going to win the Super Bowl against some very bad opposition, IF they kept the rules. But in this case the stakes and goal were far more substantial . Yet when faced with tests of character (no water or food for a time), then even after having seen such incontrovertible supernatural miracles that no rational person could deny were so, in practical terms they not only acted like atheists as regards faith in God, even to charging selfless Moses that he was out to kill them (a victim mentality they likely developed up in Egypt), but most went after false, created gods, which could not save them.
Which meant that after seeing the positive side (toward them) of the power of the one true God in saving them, they would now see the negative, that of the slaying of those who essentially were mutinous, and were without excuse.
Angry, indeed, God was and is serious about redemption and righteousness, yet merciful in saving the very ones He later weeded out, and which was just as well as necessary if the nation overall was to be saved.
As for being jealous, yes, envious no. Jealousy is wanted that which is yours, while envy is selfishly wanting what is not yours, but the motive behind the former is what matters. God simply does not need man and his allegiance, devotion or worship, and actually would spared Himself grief by not creating any beings with freedom of choice, and providing an alternative to choose fro, with consequences for both.
In short, God needs nothing, (Acts 17:25) but chose to show man His benevolence, including giving to theists the very breath they blaspheme Him with, and the sense of morality they ignorantly and malevolently charge with violating. And without any selfishness God can justly require that one uphold what one agreed to, for their own salvific purposes, and be jealous when the object of His devotion runs after the very thing which cannot save them, and will end up doing just the contrary. A good coach can be jealous for the devotion a player of potential is showing toward video games versus devotion to the team.
In commanding His people to worship Him above all else God is not being a bit selfish, as this is only right (seeing only God is perfect in power and love and purity, and unable to fail) and is what is best for man.
Also, even in the slaying of innocent people as in Joshua's conquest, God, who alone knows all hearts, was delivering - taking to Heaven - the innocent children from becoming like their generally wicked predecessors, while preventing them from further replication by destroying them (which atheists charge God with not doing).
As the giver of life God can do so, but does not want child sacrifice by man as with telling Abraham to sacrifice his son. Instead, what God wants is man to love and trust His omnipotent creator above the finite created, and thus God boih commanded Abraham to sacrifice the son God had miraculously given (and thus as Abraham believed, God could just raise him up again) and prevented Him from doing so.
As for the supposed contrast btwn the God of the OT and that of the New, the "New" is not called so as referring to this, but is as explained in a prior post , http://www.freerepublic.com/focus/religion/3718791/posts?page=196#196http://www.freerepublic.com/focus/religion/3718791/posts?page=196#196
The Lord Jesus made it clear that full devotion is also required under the New covenant, such as
So likewise, whosoever he be of you that forsaketh not all that he hath, he cannot be my disciple. (Luke 14:33. KJV)
And if thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into hell, into the fire that never shall be quenched: (Mark 9:43. KJV)
And I saw heaven opened, and behold a white horse; and he that sat upon him was called Faithful and True, and in righteousness he doth judge and make war. His eyes were as a flame of fire, and on his head were many crowns; and he had a name written, that no man knew, but he himself. And he was clothed with a vesture dipped in blood: and his name is called The Word of God. And the armies which were in heaven followed him upon white horses, clothed in fine linen, white and clean. And out of his mouth goeth a sharp sword, that with it he should smite the nations: and he shall rule them with a rod of iron: and he treadeth the winepress of the fierceness and wrath of Almighty God. And he hath on his vesture and on his thigh a name written, KING OF KINGS, AND LORD OF LORDS. (Revelation 19:11-16. KJV)
Then Moses stood in the gate of the camp, and said, Who is on the Lord’s side? let him come unto me. And all the sons of Levi gathered themselves together unto him. And he said unto them, Thus saith the Lord God of Israel, Put every man his sword by his side, and go in and out from gate to gate throughout the camp, and slay every man his brother, and every man his companion, and every man his neighbour. (Exodus 32:26-27. KJV)
Eternity is the issue here.
Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; (Acts 3:19. KJV)
Amen.