No need to check speaker wiring, amp wiring colors match harness. Plenty of info in the stereo FAQ and elsewhere on what's what.
Also, the factory sub is kinda s***. I dropped $100 on a powered sub on Amazon and stuck it in the factory amp location. Money well spent IMHO.
That static is likely ground loop from having kept the stock amp. I highly suggest bypassing it, as I did everything under the sun and just couldn't get rid of it. All of the symptoms similar to yours. Eventually just did a bit of snipping and crimping and it was right as rain.
Edit- I see...