XS Sights-adjustment

[muddywings]

Picked up a Mossberg 930 used with some XS sights.
Went out a few weeks ago and it felt like it was hitting left of POA but it was just a quick test run and I figured I was just jerking it.
Went to the range today with some slugs and with a bench rest was hitting about 8-10 inches left at 50 yards (w/ slugs) and off the target at 100. Had to aim about 12-14 inches right of the center to get it to hit center.

Looked a bit online as this is my first set of XS sights. Found an allen tool small enough to loosen the set screws but they are still in there pretty tight. I have never adjusted sights before like this. Is this a matter for a professional? From the website videos I looked like I should be able to tap them a bit.

Likewise, which way should the move if POI is left of POA?

[BPTactical]

Rear sight moves in the opposite direction i.e. if you are shooting to the right move the sight left.
Put a couple of drops of a good penetrant on the dovetail, you can even pull the setscrew and put a drop or two down the screwhole. Nylon, brass or wooden drift should do it.
Trial and error on how much movement is required.