A third way is quite simple, you could eliminate the need for a paid military and simply create a government fatherhood program, or a defence corporation if you feel the government would fuck it up.
Either way, create an organisation bootstrapped by private capital, taxes or initial contracts which:
>adopts unwanted children
>educates and raises them as soldiers
They are enlisted employees until say age 30, trained for 15 years and serving in a full capacity for another 15, after which point they are released from their contracts (or have the option to extend) into the general population as a full citizen. They will get wages, living quarters, the ability to specialise and so on. They will act first as an auxiliary support force to police and military, then later as the program expands as the defence forces of the nation.
You have saved aborted babies and provided a benefit to the country. This idea would not be supported by the public at large or the constitution as it is written, so you will struggle to pass the amendments required. We are also quickly moving towards a robotic replacement for humans in these types of work positions, so this plan would've been a lot more successful if applied about 50 years ago, when the abortion debate really hit the judicial system.
>should all people who contribute to society less than the average person be slaughtered?
no, I have given you an alternative.
There is no distinction between murder and killing, you are parsing semantics.
Aborting a child is killing it, is murder.
Fatally shooting an intruder in self-defence is killing him, is murder.
You cannot use legal inconsistencies between different states to support your moral inconsistencies in this argument. If you feel this strongly about violence, I take it you are an active anti-war and anti-gun protester? It is within your right to protest of course, and not doing so seems like a hypocrisy given your stance on abortion.