VEVOR 8FT Sliding Barn Door Hardware Kit, 330LBS Loading Heavy Duty Barn Door Track Kit for Single Door, Fit 3.7-4.3FT Wide and 1.3"-1.8" Thick Door Panel, with Smooth & Silent Pulley (J Shape)

Question should be answered by the manufacturer. But 16inches is standard.

The holes are 16 inches apart, yes.

yes. We are using it on our outdoor patio and have no problems.

Yes. I woud use this for exterior. The metal is solid and the moving parts are made of solid plastic material. I have a similar system that as been outside in all weather conditions for 7 years now with no loss in function. Even the metal parts are only just showing some minor rust.

I have not used this hardware outdoors. It has a very good coat of paint which I believe is powder coated, so it should do well in the elements but you can expect that the bearings will eventually get corrosion in them. A good maintenance plan for lubrication from time to time would be a good idea.

Yes, it can be used outdoors.

Yes it can

I think you could easily cut a foot off of each side. The unit comes with 5 standout supports 2 of which could be eliminated in your case of only needing six ft. I got mine up and it came out fine but the directions that came with it were not good. Pictures and measurements were very hard to interpret. Also mostly in metric measurements. I would suggest using them opposed to converting to inches. It is a very attractive unit when up. Good Luck