Great question. Mine has lifted extremly old nail I could not see in grass as well as 4 inch Bolts.
No it is made in Taiwan. I trust the quality of products coming from Taiwan and not China. Also in case it is not known, Taiwan is not China.
Yes. I used mine to clean area where a storage building had been torn down. It found screws, nails, bits of iron rust - anything that had metal content.
You have to pull them off by hand.
not sure on total weight, but definitely light weight and easy to carry and use.
It will pick up anything that it was designed for (nails, sheet metal, screws,etc.) I did test it, just to see how much it would pick up, and it lifted an 8 lb, 5 oz trailor hitch.
Yes, it will pick up nails in grass. However, you will need to drag it backwards, as the wheels will not help to support it in grass. Also, the magnet needs to pass within an inch and a half of the nail, so the grass cannot be too tall.