"By faith Abraham, when God tested him, offered Isaac as a sacrifice. He who had received the promises was about to sacrifice his one and only son, even though God had said to him, "It is through Isaac that your offspring will be reckoned." Abraham reasoned that God could raise the dead, and figuratively speaking, he did receive Isaac back from death".

God tested Abraham. God has some qualities that you may already be aware of. He is omnipotent, having all power, so no action is impossible to Him. He is also possessing of all wisdom, and so always acts justly. He also exists outside time (which is His own creation), and sees all time before Him, whether past, present, or future. He didn't ask Abraham to kill his son without knowing the outcome, despite Abraham having free will to accept or reject God's request (which is paradoxical, but true).

It is from this deep understanding of God's nature that Paul was able to say that God was testing Abraham. God simply has the goods to pull this "experiment" off, and furthermore, the right to, which is of course difficult to swallow for human beings who have no such capability, or grasp of how a God who is Omniscient might think.

I do agree that on the face of it that God did not justify Himself in the story for asking Abraham to sacrifice his son. However, I contest the need to ask God to justify Himself, based on who He is, and seeing the outcomes from this episode- that Abraham passed God's test, and that Isaac remained alive.

Furthermore, the reason that Abraham trusted implicitly and obeyed God without question are held in the chapters of Hebrews that the above scripture is from. Abraham in the years before this episode had such great faith in God that he picked up his entire family and lived as nomads, not knowing where he was going, but relying on a promise that God had made to him of a better future than what he would have chosen. He lived his whole life making God his number one priority above every other consideration.

God trained him as a “Father trains His son”, and at a certain point of that training, God submitted him to a test (which I'm sure that He already knew Abraham would pass) before allowing him to receive the promise that he would be the father of many nations. This is why Abraham was both ready and able to trust God's request- his faith was made strong through God's training.

This is why some commentators think that whats significant in the story is that God stopped Abraham doing it, and the torah latter commands a ransom with a sheep (much like occurs in the story) instead of sacrifice.

Now to get back to the topic:
One aspect of the story puzzles me, why didn't Abraham express any doubt or disgreement when God commanded him to sacrifice Isaac?   He did so when God informed him that he and Sarah were to have a son, and again when he tried to talk God out of destroying Sodom and Gommorah so he had a mind of his own and was able to express himself.  Yet when commanded by God to sacrifice Isaac, child sacrifice being something that God had presumably prohibited, he acted as though it were an ordinary everyday event. 

The explaination that God would make it alright by resurecting Isaac is not sufficient, God commanded Abraham to do something that was prohibited, child sacrifice and Abraham did not question this.

Way to side step the issue!  Here the ancient writer has constructed a real dilemna.  Abraham has been commanded to do something which is horrific and unforgivable – all the more so because it will put an end to his hopes of a future family.  To just say "oh he knew it would not really happen" takes away all of the complexity of the story.

This is a story to struggle with – not a story to brush aside with logic.

Can one be so willing to obey God that everything else is relitivized completely – one's morality, one's family, one's own hopes and goals?

THERE you have a tough question.  And this is the question Abraham and the readers of this story were, and are, forced to try and answer within themselves.  There is no simple logical answer to this question – it is an emotional struggle which demands growth, self searching, and torment.  If (as you suggest) Abraham knew all along that nothing bad would happen to his son and it would all be OK – none of this would take place and the story would lose all of its power.

Hence – I could not disagree more with your attempt to explaim (away) this troubling story.

As to the passage you refer to, the idea that the first born of every animal including the first born human were God’s and to be set apart, given to him in fact occurs in several places in the torah. In several other places ( Ex 13:13 and Ex 34:19-20 ) its specified that with humans the practise is done with a ransom, whereby the life of the first born son is ransomed ( or substituted) with the sacrifice of an animal in fact several other places in the torah which state the same thing show it did not require human sacrifice

Only Levites were allowed to serve in the temple.

If I asked you to give me a calculator and to do likewise with a pencil, it doesn't imply that I am bound to treat the calculator or the pencil in the same way, or infer any any way how I am supposed to use these items- I can do what I like.

The context of the verse before & after the contentious verse is helpful in deciding the intent of the author, though these statements appear to be linked to other commandments,

Exodus 22:28, "Do not be slow about making offerings from your abundance & your surplus". This most likely is with regard to agricultural surplus but the gist is to sacrifice out of love and of fear of the Lord.

Exodus 22:30, "You must be a people consecrated to me". Providing a son to serve in the temple fulfills this requirement in triplicate, by sanctifying the family who provides the son to serve. That family is tied to the temple by blood, and the Lord repays the family that does this, as shown in the story of Hannah above, when she is given more children by the Lord to make up for the loss of her son.

Hope that helps