your 3 arguements towards the seperateness of the fetus is at best weak

1. The second entity – the fetus – develops into a unique and different person. Not sometimes, but all the time. No human fetus grows into anything non-human.
   
   Depends on how you define "non-human". An entitiy with no funcitoning CNS and no limbs would not be conisdered "human" in the common understanding of this. OTOH if you are going to rely on genetics to determine what is "human" then the skin cells that you slough in bed are equally separate and equally pluripotent (both require specific sequences of hormonal baths to develop into what is considered a human being).
   
   If you cannot differentiate between a sloughed skin cell and a fetus then you don't have a case to make on distinction basedin science.
2. Unlike other entities of the mother’s body, or other cell configurations, the fetus does absolutely nothing biological on behalf of the mother. There are never any biological conditions within the mother in which her body’s response is “grow a fetus.” The fetus is not a biological response to anything. It has no biological function on behalf of the mother. It is entirely a non-mother-oriented entity.
   
   The same holds true for a tumor. A tumor does absolutely nothing biologically on behalf of the host womnan. There are never any biological conditions in which the body's resonse is to "grow a tumor". The tumor is not a biological response to anything, ithas no biological function on behalf of the host woamn, it is an entirely non-host related entity.
3. At its earliest stages, the mother’s body supplies the development work, but that work is on behalf of the fetus, not the mother
   
   At its earliest stages the host wonan's body supplies the develipment work but the work is on behalf of the tumor, not the host woman.

So there really isn't a lot of discussion to be had here. You've not created a biologically based distinction between a fetus and a tumor.