Hi DreamyEye ~
Both of your questions are interesting. Other than offender profiling, my other main interest is crime scene analysis. (Not to be confused with crime scene investigation). Often, offender profiling and crime scene analysis overlap. The reason I am mentioning this is because to answer your questions, one has to consider both the profiling and the crime scene analysis aspect of this case. After studying the crime scene, I believe the following to be true -
1) Taylor was the main target. Skyla was murdered simply because she was in the wrong place at the wrong time.
2) Both the girls could identify the shooter and therefore, once the shooting started, he felt it necessary to silence both of them.
3) I do not believe Taylor was shot because of rejecting someone romantically / sexually. However, I believe she belittled / disrespected him and this was what triggered his anger. The individual does not like feeling less than respected and when he felt disrespected, he reacted in an extreme manner. His extreme anger may have been precipitated by drug use. This individual may have recently been fired from his job, broken up with a girlfriend, argued with a girlfriend, etc..... Something, that made him feel 'disrespected', and when Taylor disrespected him, he took his anger out on her.
4) Two firearms - traditional profiling and crime scene analysis would say, if there were 2 guns fired, there must have been 2 shooters. I am still not sure whether I believe there were one or two shooters.
5) Taylor was shot mostly in the face and at least one shot was in the groin area. (iirc) Again, with Taylor being the main target, I am not surprised by these shots. This offender wanted to belittle Taylor. What better way than to mark her facial features with violence and to 'sexualize her in death'?
I hope I answered all of your questions. Please remember, all of the above is just my opinion. It is not based on scientific fact.