Motor oil questions

The problwem with running synthetic past 3000(or 5000) miles is not that the oil can't do it's job. Synthetics can actually last up to 10,000+ miles but you get too many contaminants after the 5k point. With mineral based oils they lose viscosity and become contaminated by 3-5k.
As for changing to 10w-30 or 10w-40,with synthetics you may not have a choice,I've only seen 5w-30's. Regular oil I wouldn't recommend it cause ford has done alot of research to see what works best in all conditions. I don't think you'd hurt the motor but you might lose some power due to the heavier weight.

Depending on your year of car, 5W-20 is "recommended," but there are only a handful that make that oil.

Just get a jug of Mobil 1 5W-30 from Wallyworld, a Motorcraft filter, and don't look back.

As many others will tell you, the difference in the oil is minor, and was only done by Ford to meet certain requirements.