I always play through a game on Medium first, just to get a feel for it. Like some others here, though, I've played through JK several times on the Hard setting. Sticking to the lightsaber makes it more challenging. And Jedi Boxing is fun too.
That's how I took out the Gamorrean guards in MotS the first time I played it...you just have to be fleet of foot to avoid their staves. I have to admit I haven't completed either JK or MotS just using fists, though...but then, I've never really sat down and tried.
The best way I found of tackling Boc is to circle-strafe him as fast as possible and keep slashing him from the side. Don't let him get too far away from you, or he'll leap in swinging both lightsabers.
And yeah, keeping Jerec away from the tower is key to defeating him.