Hypos: 804 Dying Declarations

Professor Colin Miller at EvidenceProf Blog has written a great article on an 804 exception to hearsay: Dying Declaration.

I have never written, or even thought that much about, this exception. It is rare that it comes into play, but every now and then you will see it. After reading Miller's post, I learned/realized that for the exception to apply the crime has to be homicide (we'll skip civil cases for today). His post compares the Federal Rule to California's. South Carolina follows the federal requirement of a "prosecution for homicide." I do not know the history of this rule, so I am wondering why there is a requirement for the crime to be homicide. I am also wondering if the death must be the actual one that the defendant is being prosecuted for. Think of these two hypos:

1.) Defendant is on trial for attempted murder. He allegedly shot the victim. At the hospital, the victim states to the doctor that he knows he is going to die. The doctor confirms that to the victim that he will likely die. The victim then states, "the defendant did NOT shoot me." The victim slips into a coma and is still comatose. At trial, is the defendant forbidden to enter this statement by the victim? (Does the victim have to actually die, or just believe they are going to? What if the victim in this case woke up from the Coma, but died later in a car accident?)

2.) The defendant is on trial for murder of John. The State wants to introduce evidence that the defendant shot and killed a different person, Paul, years before he allegedly killed John (Assume that this evidence passes 404, 403, etc.). The evidence of Paul's murder is a dying declaration by Paul that the defendant shot him (Again, assume this passes 804 requirements). Can the State introduce this evidence in the defendant's murder trial? What if the defendant is on trial for attempted murder of John?

I have two questions about this 804 exception: can it be used to prevent a defendant from exercising their due process or other rights (victim stated defendant was not shooter)? And second, does the statement/declarant have to be the actual victim of the prosecution's case?