I have read through this entire thread. I'm new here. Let me preface this by saying that I am from the area and I'm about the same age as the victims. I familiar with the location as I also partied in that area in the late 80's. I had some thoughts. At one point, I considered whether the killer could have hidden in the back of the car at the club and as they got in, held a gun on them and forced them to drive to the Enclave. Looking at a picture of the car, it seems unlikely because it's pretty small, but not impossible. I'm only bringing that idea up because I haven't seen it mentioned as a possibility before. It is probably more likely that they were just out there to make out and the killer came upon them, whether from following them from the club or as a crime of opportunity. I remember from my partying days that because it was so secluded and empty, it was very obvious when there was someone else around and we were always worried about getting caught doing whatever it is we went out there to do, so we kind of kept an eye out. At the time, there were just a bunch of empty streets and NOT a lot of trees. This was not a dense thicket they were parking in. In fact, they had to walk a bit of a ways to get to the tree line. So, even if they were making out with music on, I would think that it would be more difficult to sneak up on them.
Next, my armchair psychology profile of the killer: the overkill throat cutting of Andy speaks to me of rage, the 3 (?) lighter slashes on Cheryl speak to me of indecision or like he was working up the courage to make the kill cut. Especially if this was his first actual murder? My feeling of the timeline would be that there was one perpetrator, he had a gun AND a knife, he forced them out of the car at gun point, walked them to the tree line, had Cheryl tie up Andy, led Cheryl away, raped and killed her, came back and killed Andy all hopped up on adrenalin. What is interesting to me is that he wanted Cheryl to be found but also covered her with boards, almost as if he was ashamed of what he had done and didn't want to look at it. Then, covered with blood, he goes back to the car, leans on the seat rest to pop the trunk or reach in the back(getting blood on it), takes out the golf club and balls, (getting blood on them), and lines them up pointing to Cheryl so that she is found. I think the balloons were already there and probably just caught up in the trees at some earlier date and he may have arranged them to further point to Cheryl. I'm not sure about the twenty dollar bill. Could be a red herring, could be to show disdain, could have just fallen out of her bra. I'm not convinced Cheryl having worked at Rick's briefly as a waitress over a year before is even relevant. It's tempting to try to connect all three victims through strip clubs but that may be pure coincidence. Texas being Texas, strip clubs are everywhere and I'm sure everyone knows someone or has some connection to them.
As for the previous rape case, the fact that he was already in the boyfriend's house could explain him knowing the boyfriend's name. He could have known the boyfriend and was surprised by the rape victim while trying to rob the place or he could have seen the name of the boyfriend on his mail. The fishnets over his face could have been something he pulled on when he was surprised by the victim being there. They might have been left by the victim in the house at a previous date. Not sure he would have planned to use fishnets. But, yes, fishnets would not have been unusual in the goth/punk scene at the time, as well as being something a stripper might wear.