Parking lot practice may help as well.
Keith Codes Twist of the Wrist II will help alot.
The tight on the bars and timid reaction are survival reactions. WE NEED SURVIVAL REACTIONS TO LIVE!!!! The problem is they all work against proper operation of a motorcycle. Lucky for us we are Human and able to use our brains to control our actions IF IF IF we practice and plan.
(PS you can brake in a turn while leaned over) I do it alot on purpose to practice that skill. You will be amazed at what you can do with a bike as long as it agrees with motorcycle design.
Its a sliding scale, if you are using all of your traction to turn of course you cant, but you should never be using all of your traction to turn on the street. Gotta keep a reserve for oh I dont know braking and all. LOL LOL