I agree with your foundation but not how you arrived there. Murder is spoken plainly, but not abortion. Where is abortion dealt with in the Bible? You started with a theology to prove a point not the foundation. That is like building a home on a foundation that someone else may have started and it may or may not be adequate. I am unable to see how you developed murder and abortion as synonymous. The Bible says that God breathed the breath of life into them. Some well known preachers such as Criswell and others at the time did not believe it was a baby until it was born. Therefore abortion was not murder because the baby was not born yet. Is not abortion pre-birth?
Its murder. You can muddy the waters all you want, but abortion is just a name for a KIND of murder. Since the Bible forbids ALL kinds of "murder", ir is forbidden. THAT is the foundation. Saying, "Well, its not a baby till its born," is what is starting a theological stance to prove a point. The burden of proof is on the individual that a certain kind of person, is not a person. I don't have to try to defend unborn people, or black people, or Asian people, and try to show from the Bible that they ARE in fact persons. That is just absurd, and I don't care who says what.
Is it a baby because it did not have the breath of life in it and did not live?
Unborn children breathe through the placenta. A human being cannot survive without a continuous supply of oxygen. Again, you are attempting to shift the burden of proof.
I just do not believe that you can be anti-abortion directly from scripture. Is it wrong to abort a baby because it endangers the mother?
Sure you can. "You shall not murder."
As far as the other, killing someone who is endangering your life is not murder, according to the Bible.
I think many Christians miss one important thing. That is that God places importance on some things above others. Is it more important to work at a hospital and miss a sabbath/church or is going to sabbath/church an absolute.
Ex. 20:8 "Remember the sabbath day, to keep it holy."
How would you support priorities in that situation directly from scripture.
Mar 3:3 And he said to the man with the withered hand, "Come here."
Mar 3:4 And he said to them, "Is it lawful on the Sabbath to do good or to do harm, to save life or to kill?" But they were silent.
Mar 3:5 And he looked around at them with anger, grieved at their hardness of heart, and said to the man, "Stretch out your hand." He stretched it out, and his hand was restored.
That is very plain, and applies directly to the situation you quote.
However, dealing with a situation where two Biblical commands compete, is COMPLETELY different than inventing a commandment out of thin air. Gambling is not only nowhere mentioned as a sin anywhere in the Bible, it is not even alluded to. There is literally NOTHING about it. We DO see, however, places in scripture where so called "games of chance" are used by Godly men in good ways. The Urim and Thummim, for instance, or the drawing of lots.