It might be helpful to understand you better if state your premesis and conclusions in argument form, without all the cruft. But, I'll try to address the main themes in your post here.
Does love exist?Yes. I'm perfectly happy to say that the term love refers to purely material processes involving the endorcrine system. I think it could be arguable that love also incorperates patterns of behavior that are independant of what your endocrine happens to be doing at the moment, but in either case - its all fits neatly inside materialism.
I'm also perfectly happy to acknowledge that many people do use the term love to refer to something that isnt real. So shame on them. I'm not doing that, however.
So to end this portion of the post on a note agreement, we do seem to both think that the term love refers to a material process, or in your words "a survival reflex". This is fine.
Can new properties arise that arent inherent in "the being" of its constitutients?Of course they can, and it should be trivially self-evident. Forget love and emotion for a second. Can a single h2o molecule scratch its back? Of course it can't. They don't even have backs. Nonetheless, certain arrangements of mostly h2o molecules do have backs and can scratch them quite easily. There are at least two new properties gained there: a) a back, b) the ability to scratch it.
Can a single h2o molecule think? Not that we know of. Nonetheless, certain arrangements of mostly h2o molecules do think. Empirical fact.
Unless you can show otherwise, these counter-examples are fatal to the argument that properties of the whole must be "inherent in the being of its components". The matter that combines to form the systems we call people, has been here during the entire lifespan of the universe after all - and it certainly hasnt always had the same properties that people have.
As a matter of fact, the argument you have been presenting on this point is a clear-cut, text-book example of a
fallacy of division.
Therefore Nihilism, Oh noes!?As a point of agreement, I will concede that there is no ultimate cosmic purpose. No Thing (ie creator being) wants us, or created us. While there is no ultimate purpose to the cosmos, purpose and meaning certainly exist, in localized prudential forms. In fact, unless you commit yourself to an infinite regress, there has to be a termination point for purpose, beyond which it is incoherent to require further purpose (same for meaning). Yet the question could be easily asked "What is its purpose?", and one would easily have to say "There is no purpose for this thing". That termination point, from where I sit, seems to be the mind of a sentient being.
Our minds conceive of and move with purpose. One might even say purpose, like back-scratching, is an emergent property of sentient systems. So its with no problem what-so-ever, that I say love is meaningful and filled with purpose, to me. Whether the cosmos agree's, well... I can't see why that even needs to enter into it.
To sum it up, one might say that minds exist for no purpose, but in existing, they certainly gain purpose and meaning.
Question: Can love exist in some possible universe?I was not restricting you to materialism here. I was seeing if you think meaningful love can exist in any possible universe, a theistic one included. In part, this is simply to get a better idea of what exactly you think love is supposed to be. So how bout it?