For problem #1, I opened the cases again and moved the speaker wire away from the metal box. Also made this wire not so parallel to the other one to reduce interference. The noise is now entirely gone. Very happy.
For problem #2, I used some window/door sealing strips to add about 6 mm depth to the cups. Now my ears won't touch the hard surfaces and I won't get sick after hours of listening. The magnets and three teeth still hold the cups quite well in their positions. Look good too!
You may watch this video for more details:
Now this Harman Kardon is perfect: sounds the best, noise free, comfortable, long battery life and wireless; cannot get any better.
[update]The 6 mm white strips still cannot add enough depth. After few days of use, they were pressed down to 4 mm or so. My ears still hurt. I removed them and used the 5/16" strips. 5/16" is 8 mm, not much thicker than 6 mm, but it is wider and firmer - won't be easily pressed down. I first taped the strips onto the ear pads, then I used several pieces of double-side tape to hold them on to the body. The double-side tape should be very thin and cut to be narrower than the strip so that the strips will still seal well. Without good seal, sound becomes thin and lack of bass.
Abstract in Chinese