Round #2 of BioShock: Infinite Complete. Still confused.

Last night I finished my second full playthrough of BioShock:  Infinite.  I enjoyed it just as much or more than the first time.  I upped the difficulty for this playthrough and found the combat slightly more challenging, but still doable.  1999 mode is my next option.  Even though I finished the game again I am still not 100% clear about the ending.  (Spoilers.  Big spoilers.)

Firstly I must express my complete respect for the powers of Elizabeth/Anna.  She's no superhero, but seriously, the ability to alter time and space has got to be the most amazing set of powers.  After you destroy the siphon she can enter any world that ever existed.  That's....just....so awesome but so confusing.  It's the same confusion I had with the Lutece twins who are technically dead in one of the versions of Columbia that you enter--but they're obviously not dead because they continue to pop up and give you helpful tidbits of information from time to time.  How are they alive in all these possible worlds?

The whole part with Elizabeth/Anna's origins is also confusing.  If Booker is really Comstock then he's stealing his own child?  Where did this child come from?  Did Booker steal it?  I don't get it.  What did the Lutece twins have to do with it?  They designed the device to allow Comstock to go back and get Elizabeth/Anna.

Let me piece together what I think is going on.  There is an initial reality with Comstock and his wife--no baby.  Rosalind Lutece is doing all this quantum physic-y stuff and creates not only the ability for Columbia to float but also the device that creates the tears between worlds.  In doing so she opens an alternate universe where Booker/Comstock has a child.  The real Comstock decides to steal the baby (Elizabeth/Anna) so he can raise his heir to be his successor.  Elizabeth/Anna possesses some special abilities (how she acquired these abilities is also questionable--a result of her exposure to Lutece's device?).  As she matures her abilities develop and Comstock is forced to use the siphon to keep her under control.  Rosalind Lutece sees what Comstock has become or feels some guilt and decides to use her device to bring Booker into the reality with Elizabeth locked in the tower.  Rosalind and Robert Lutece falsely plant the idea of freeing Elizabeth with the intent of Booker breaking her out and unleashing her full powers.  Then Elizabeth can use her powers to eliminate Comstock once and for all.

My one last lingering question is about Elizabeth's existence.  Would she still exist if she killed Booker/Comstock?  Wouldn't she be eliminating her own presence?

Never has a game made me puzzle over so many of the details.  I want to figure it out. Maybe I'm weird that way....