1. It is the best digital detector I have owned. But that should be taken with a grain of salt as I have not owned a higher end machine.
2. At least with the stock DD coil...... no. I air tested a 2.5 mm nugget and get a reading at only 2". I would be curious if a sniper coil would improve things.
3. Yes it will find junk... and in truth, at the beginning, you should be finding and digging junk, and then as you learn the VDI you can notch your junk out.
On a side note. I have used this in saltwater. I was surprised how well it did. If you ground balance often its very manageable.... for single freq VLF.
The big selling point of the AT is that you can dunk it, get it muddy and hunt in a hurricane.