Well with the last like 5 updates of this CM7 rom usb has been working... maybe you have an old copy?
And no CM7 rom will charge with the phone off. yeah it's a pain, look for a charger that is at least 1 amp, my phone charges completely with a 1 amp charger in just over an hour.
And if you had no reboots on a stock rom, then you must be missing something while installing the others. All other roms make my phone more stable than the stock one was, and I haven't had a single reboot since the last time I flashed, which was weeks ago...
Why don't you tell us in detail the process you are using to flash the rom? Maybe you have overlooked something...