horizontal receptacles and stud location

I am trying to avoid drilling into any wiring when I put some anchors in the wall to mount a wall lamp.



Question 1: I live in a NYC apartment built in the 60s. Most of the receptacles are horizontal. Would these still be oriented on the stud the same way a vertically mounted receptacle would, and I can assume a stud would be located adjacent these receptacles on one side?



Question 2: if I am not drilling into studs, how can I be sure there are no horizontal running wires that may be running to the next outlet behind the drywall I am drilling into?



Question 3: What is the typical depth before one would hit wiring behind the wall? I'm not worried about my anchor screws, as they are very short, but my drill bits went into the wall about 2 - 2.5 inches, and I hope I didn't nick any wiring.



Question 4: one screw went in really smooth. The other screw, after the drywall, had slight resistance. I am 99% sure there was no stud there, so what could it have been? Hopefully not wiring!! What you think???



I should have considered all of this prior to drilling, but dumbie me. :(



Are there any decent wiring locators below $100? So many mixed reviews.



Thanks!!

horizontal receptacles and stud location