My house is located in Washington state and is wired with ethernet and coaxial cable to several rooms. I am hoping to mount my TV on an exterior wall. I've been looking for studs using a Zircon MultiScanner A200 stud finder, which includes a built-in live AC wire detector. There do appear to be some consistent studs with 16" spacing, but the other results I'm seeing are a bit confusing:
The dark gray dots indicate locations where the "StudScan" mode detected the center of a stud. The yellow dots indicate places where it displayed the symbol to indicate the presence of a live AC wire.
The results in some locations were very inconsistent, which I've indicated with ovals in the photo. Particularly the live wire warnings wouldn't always reappear when I moved the stud finder off (still against the wall) and back on to the same location, so I'm not confident in the accuracy of any of the yellow dots. (I also saw brief flashes of the live wire symbol in some locations that aren't pictured — these are just the ones where I saw slightly more consistent readings.) It seems like there is more empty space between the centermost two studs, which are likely the ones I would want to use, but there still might be some wires there.
The other side of the wall looks like this, with our main electrical breaker and gas meter. There is a breaker box inside the house, one floor up on the opposite side from the TV.
How safe or unsafe might it be to drill 3.5" or so into the studs I found? Why does there seem to be one stud about halfway between the usual 16" spacing? Would the electrical wires, ethernet/coax cables, etc. be located near the sides of the studs, between the studs, in front of the studs, or what?