Idioms and Story Setting

Just as I was wondering whether I should set aside my novel for a while and work on this blog entry, I read a post by an author friend of mine, Bob Spear ( http://bobspear.wordpress.com/ ), and felt encouraged to go ahead with it. His article emphasized the importance of accuracy in the setting of a story; mine touches on a related subject.
Needless to say, getting all the historical facts and locations right is crucial, especially when it comes to historical or semi-historical novels. This, however, is only one of the challenges. Another one is the avoidance of unsuitable idioms.
As I progressed with my story and created inner monologues for my characters as well as conversations between them, I realized that many of the expressions which are commonplace today could not have been part of their thoughts or speech. And being something of a purist, I felt compelled to stay away from them even in passages which did not describe things from their point of view.
Following are just a few words and idioms which, in my opinion, have no place in a novel that is set in the time of King Solomon (about 3000 years ago):
Solomon, for instance, could not have 'steeled' himself against something, because steel, although found in very small quantities in some archeological sites, was not widespread enough to have given rise to such an expression.
Neither he nor his subjects could have been 'mesmerized' by anything, because Dr. Franz Mesmer, from whose name the word is derived, lived in the eighteenth century.
Two people who agreed on something could not readily be said to be on the 'same page', since books in those days did not consist of bound pages but rather of scrolls.
Could Solomon have 'exploded' with anger? I am not sure. After all, explosives were only invented some 2000 years later.
Could he have complimented a smart person by saying that he or she 'had a good head on his or her shoulders'? Unlikely. The functions of the brain were not known at that time, and thus no one would have made the connection between head and intelligence.
I could continue this list with dozens of other examples, but I think I made my point. Just for fun, though, let me just mention that the expression 'three strikes and you are out' does not occur anywhere in my novel, because I have it on good authority that baseball was not being played at Solomon's court.
There is one instance, however, where I am afraid I won't be able to resist the temptation to use an improper expression. I am referring to an idiom that is most likely linked to the convention of putting 'North' always at the top of a map and 'South' always at the bottom, which eventually gave rise to the term 'go south', meaning 'to go down' and thus 'to go bad'. That kind of standardized layout did of course not exist in the distant past, but here's the thing: Solomon's misery began when he got dumped by the woman he loved, namely Makeda, the Queen of Sheba, who was also known as the 'Queen of the South'. How, then, can I not have him say somewhere that things started to 'go south' for him when that was where Makeda decided to return? I have no choice there, do I?