i don't think you have to worry about them piercing an artery and killing you because they seem to know how to make you miserable without killing you, indeed it seems to be their job, the ones that pierced arteries died along with the host, and the one's that avoided piercing arteries survived to have more babies, that is how natural selection works
and if you they do know how to make the blood clot, which would not surprise me in the least, because it think they cause constipation to prevent you from pooping them out, then they will know how to make a clot form around a puncture wound
if I could bear the pain I would try to scoop out my rectum with a spoon and see if I could get some of them to come out with it
yes i believe your body will break down and haul off the rotting dead corpses for you but you might feel a little achy or woozy while the clean up is going on maybe need some kidney and bowel support