About hardware lights, don't set auto-brightness on, try moving the brightness slider a little.
Camera is working for few not not for others. And why isn't V3 camera installing, did u try installing it as an app? If so, don;t do that, instead push the V3 camera to /system/app, set the permissions and reboot. While you are at it in recovery, go into advanced and fix permissions. You 1st said themes aren't working and then that you got it working, so I;m assuming you got it to work. About lockscreen wallpaper, place all the pics u want in /system/media/theme/lockscreenwallpaper and now apply from theme manager.
Let me know fixing permissions helped MMS. I don't use it but people reported it to be working.
I do have auto brightness set off but i still have the issue but i did try and install it as an app since i dont have a real computer to speak of atm. But once i do i will try to push the camera and fix permissions. Themes still wont install, they aren't found when placed in the 'system/theme' folder but they do in the MIUI folder on the sd card but dont install. I did a clean reinstall so ima try the permission fix then report back.