Depending on your cellular provider they usually have sim card poppers to open the sim card tray. It is pretty easy to get open with one of these tools. A cool trick to use to open the sim card tray is using a clothes pin if you don't have the same tool accessible that the cellular company would have. There usually isn't a cost associated unless it ends up being physically damaged. Hope this helps!
Yes I would agree with John also when you did repair, did you take a picture of all parts? I usually do this one to for my own assurance, also just in case something looks different next time I work on it. Sometimes frame damage can be a big factor in the screen not applying all the way as well. I would also take a look at the frame, as well as what John suggested.
Very hard to tell but when you did glass only repair how exactly did you take off glass, only reason why is applying any type of glue may damage the phone more which is another story. I wouldn't apply any glue to the iPhone. Most repair techs i know use loca for any glass only repairs.
I would try to realign the flex cables and make sure they are pushed in sometimes when they aren't pushed in fully you do get a dead screen. From what it looks like the cables aren't bent which is a good thing, when you worked on the phone did you notice any static or shock while working? If so you may have shortened one of the components in the phone as well.