I find "attraction of opposites" again a very cerebral statement, as if looking to a phenomenon as an outsider. Though it holds true as a scientific abstraction, we can see an attraction in an ascending order of refinement, also literally speaking as far as the chakras concerns: from carnal, to being in love with someone, to platonic love, to love for animals and nature, to warm sympathy and compassion, to divine love.
Not necessarily. Scientific Illuminism shares a lot with science, and although there are Thelemites who view the Thelemic pantheon as just that, gods, a great many view it a scientific principles describing forces at work in nature. Generally speaking, everything that happens, everywhere, is the result of the interplay between Nuit and Hadit. Nuit is the all-encompassing expanse (perhaps "space" could be a good term for it) Hadit is the infinitely contracted point, the force, the experience. Since Hadit is the flame "in the heart of every man," everything one does plays out the pageant of Nuit and Hadit communing.
While Crowley liked to explain these doctrines through the use of sexual imagery, this does not mean it is relegated solely to sex, but it also does not mean, in my opinion, that this is only divine love. The card Lust, crossing the Priestess at the location where K&C happens, depicts the feeling one gets when carrying out one's True Will, that certainty and ecstasy. Theoretically speaking, when you do your Will, even doing something mundane like washing the dishes feels ecstatic, like the best love you've ever made. The dishes are made clean by an application of Love, shown in the energy of scrubbing. You are the Hadit swimming in the expanse of Nuit's dirty dishes.
Now, when it comes to the attraction of opposites, this has to do with the doctrine of 0=2, and the Thelemically-updated IAO formula. as in two opposing forces interacting the annihilate each other (the dirty dishes vanish and cleans ones are left in their place). Firstly, this is also reminiscent of transforming every act into a meditative one, as the application of Love becomes paramount, rather than the result. Secondly, as you are Hadit, every act you do is, in essence, "making love" to Nuit, and should be treated as such. Everything you do is an act of ecstasy (because it your Will).
The IAO formula comes in the principle of conservation of energy. In the old Aeon, the doctrine of birth, death and resurrection was used to explain everything from the changing of the seasons to a man's life. The Sun was seen to die in Winter, only to be reborn in the Spring. After performing, the phallus was seen as dead and spent. However, since we know now that the Sun does not die, that formula no longer works. The new magickal formula takes this into account, and the result is not the Dying God, but the Everborn Ra-Hoor-Khuit. Mundanely explained, the force you exerted in washing the dishes isn't gone, it has merely transformed (into clean dishes). Going back to the imagery of love-making, Sex Magick operates on certain principles, one of them being that in orgasm one feels a disconnect from all duality and feels Unity. Since that is the result of making love, and all actions are the result of applying Love to something, then that feeling of unity, plus the ecstatic calm that comes after, are what it is all about. The phallus is not dead, its energy has gone into something else (illustrated by the Hanged Man) and has most likely made children.
Why should Love be under Will?
Maybe Crowley's creed was above all inspired by his despise for christianity, and is no iron law.
Because although they may seem different, they aren't. Although it is true that Crowley had no love for Christianity, it is a simplification to describe the Book of Law solely under those terms. There is also a feeling that in his writing (not the delivery of Aiwass) he does differentiate between the religious institution, and the magickal doctrines inherent in religion.