A Consistent Ethic of Life

I've been engaged in some interesting discussions on a site for atheists- Why Wont God Heal Amputees. There was a discussion about abortion, and amazingly enough, I was seeing many of the same woo-based arguments against abortion there that I hear from people heavily invested in religion. It set me to thinking- why haven't I set down my exact beliefs on the value and hierarchy of life? So here it is- my (hopefully) logical and consistent ethic of life.

Life is important to me, because it is the only state of being I know. Non-being is frightening to me because it will deprive me of relationships with other living beings and I will cease to be an agent of action. I assume other people feel the same as I do, as they seem to fear the finality of death, too. I imagine other beings share some of these feelings to some extent as well. Therefore:

I reject killing anything that I do not have to kill. For beings that I am reasonably sure are non-sentient (insects, etc),my threshold for killing is convenience. I will not kill a thing that I am reasonably sure is non-sentient unless it inconveniences me. Example: Spider crawls down the wall. If possible, I catch it and put it outside. If it won't go, or I can't catch it, I kill it. I will preemptively kill non-sentient things if I suspect they may cause me or someone/something I care about harm or major discomfort. Example: I put flea treatment on my dog and cats.

For things that have very limited sentience, my threshold for killing is extreme inconvenience or suspicion of harm or discomfort. Example: a mouse gets in my house. I would try non-lethal traps first, but if I found they were hard to operate or weren't effective, I would call in an exterminator. If I felt there was an infestation, or that the presence of a mouse might compromise my family's health, I would skip to the exterminator.

For things that have some level of sentience, my threshold for killing would be immediate danger. Example: A strange dog comes into the yard, growls, corners my son- I grab first available weapon, and use whatever force is necessary to secure my son's safety. If the dog dies in the process, I have no regrets. I would not kill an "unrurly" or misbehaving house pet unless it became an immediate threat.

Probably fully sentient non-human beings such as great apes or some cetations- I would not kill unless I feared that they were going to imminently attack me with the intent to kill. I would first aim to incapacitate the animal, reserving lethal force as a last resort.

I would not attack a sentient human being with the intent to kill unless it attacked me first, or I feared such an attack was imminent. I would only use lethal force if I felt I had no other resort.

Special circumstances: With regard to abortion, I classify embryos/fetuses as non-sentient beings, and would use that standard. People in a perpetually comatose state or vegetative state, or otherwise totally impaired, would fall under the some level of sentience guidelines. As they would be unlikely to present imminent danger to me or mine, I wouldn't personally kill them, but I would support termination if it was shown the chances for them regaining sentience were minimal, and their continued maintainance was a possible detriment to other people. I would not actively kill or have an animal killed for food above fish, possibly fowl level unless I felt it was necessary, though I will eat food products from higher animals(beef, pork, etc.) that were all ready killed for consumption.