Subaru decided it would be a good idea to have an odb style port but use completly different software. All jap cars pre odb2 used something i can't remember the name of, you can get a scanner but they cost over a ton.
As gambit says theres should be 4 diagnostic plugs a little further back from the port you were playing with. I'd paste the guide link in but i'm on my phone :-(
Maybe a flat ish battery, i'd either hook it up to a charger for a couple hours or go for a nice long run with your side lights on see if that cures it. Cheapest options first.
As for idle at start up it should idle high then drop to 750ish takes a couple of mins.
If charging the battery hasn't cured it you could try the un plug maf sensor test. Not exactly a very scientific test but if you un plug it whilst the car is running it should stall. If not it's a bit dodgy and needs replacment.