Ubiq.
There is no such חוות יאיר. True he goes through כדרך הלומדים various קושיות and סברות to answer those קשיות. But l’maskono he paskens the Rambam Rashi and Tosfos who klor learn the sugya in Sanhedrin as רציחה ממש. No one ever quotes any rishonim who argue these Poskim. The acharonim only deal with kashyas (like the Uber of a sotah) and try to resolve them with the osak of the Gemorrah in Sanhedrin.
The maharit you quote is completely סותר a different teshuva in maharit and what he writes in the Teshuva you are quoting is so vait that R Moshe says it was a talmid “טועה ומטעה” who wrote that teshuva. R Moshe (as well as R Unterman) point out that in that same teshuva he quotes a ridiculous teshuva of the Rashba claiming that the Ramban was advising a non Jewish woman ato have an abortion. RMoshe and R Unterman both point out that no such teshuva exists in our Rashba and have no hesitation in saying that is was just a ruse that this טועה ומטעה was מזייף.
Interestingly, at the end of the Teshuva R Moshe says שרי ליה מאריה on the ‘חכם אחד’ who was matir. He also says that this חכם אחד’s chiluk of seven months is just made up out of whole cloth. It has no basis in logic or kabolo. What? Bc at seven months in chazal an Uber is considered viable? What nafka mina does that have ? If it is only a חבלה go up to 9 months. The whole thing is simply ridiculous.
R Moshe , שלא כדרכו, goes out of his way to denounce what is happening in the world regarding the zilzul in רציחה ממש which is abortion.
He was clearly unnerved at this new low in basic morality.
Also, This contradicts Tendlers tzu shtel of what R Moshe probably did say about generally not wanting the Malchus to get involved in religion even if we agree e.g. forbidding an assur type of contraception. Abortion is not a specific religious issue. It is basic morality. To practice it the way it is practiced today is the depths of depravity and how could anyone especially a Jew who claims to be in favor of Hashem and His Torah be in favor of depravity.
Btw, you didn’t answer many of my kashyos on חבלה which is fine. Just know that R Moshe (and re some of them, Tosfos, the חוות יאיר as well) who make these points as well. Not to answer Them is not so fine.