Yes there are multitude of natural family planning options all of which require abstinence at some point. So spilling his seed was only bad in this instance? Is that your argument?The calendar method is a natural form of contraception, there's condoms, and in Genesis 38:9-10 you see the obvious non-invasive method that they used at that time- Onan was only in trouble with God because he was told to procreate in this instance.
You can laugh, but my grandmother had to give up her own children and had ten all together at home, two had passed.
As to your grandmother I'm sorry to hear that but exceptions don't negate the rule. The vast majority of abortions are not performed because someone is afraid they will have to sell off their babies, they are performed for convenience. Period.

