I can only share what I have done with my phone. I'm sorry that I don't have all of the answers.
For 1. I wouldn;t see the difference. I used a USB cable. If you already have the bluetooth stuff, then try that. At least it will save you the cost of the cable. If not then I figure that the USB cable for the unit is cheaper than a bluetooth adapter.
For 2. You are right, it is a MiniSD card that goes in. I'm not sure why in Diego they refer to a MMC. Maybe a series of phones used MMC cards and the theme stuck. I don't know.
And for the activation codes, the Diego is the work around for that. IF you change the setting, then the list will remain empty and you can use mp3's as ring tones. I actually have a clip of Captain Hero from Drawn Together as mine. I can also now play Mobile Java games on my phone too. They are more than just invalid apps. The reason it says that is because of a setting that denies you to use games on the memory card.
I hope this clears up some things for you..