1. The range is unknown, but it can vary depending on the power input I suppose. However, the largest field ever recorded in recent history was made by Centerpoint Station. It blanketed the entire Corellian system under an interdiction field of several light-months' extent.
2. The CC-7700 Frigate is one such vessel yes. Not sure when it was developed. It first appeared i think in the game Rebellion (Supremacy), most likely as a counter balance to one of the Imperial Interdictor picket ships that was used in the game.
3. All hyperdrives are equipped with a safety system that detects objects in real-space. Objects in real-space effects hyperspace by projecting the bodies gravityfield into it. In hyperspace this is called mass-shadows
When a mass-shadow is detected, the hyperdrive shuts down and drops the ship back into realspace.
4. The Empire deployed their first interdictor some months after the Battle of Yavin. It was designed and built by Seinar Fleet Systems, one of the 3 major companies contracted by the Empire at the time. The first Death Star is reported to have atleast one experimental prototype generator, but it was highly unstable at the time. When activated without elaborate safeguard systems it was prone to catastrophic implosion leading to black hole formation.
Gravity Well Generators arn't really a new thing. You might say it has been re-invented in recent times. Centerpoint Station has the oldest known Gravity Well Generators.
5. Don't have any sneaky things really.