I don't have Mi Pad / 2, I have Mi4. The ways are the same for all devices. I'm pretty sure I could help to fix anything if I would have the Mi pad with me.
For rooting you need to install Supersu.zip via TWRP.
"SuperSU download"
Root Checker for check if your Mi pad 2 is rooted: https://play.google.com/store/apps/details?id=com.joeykrim.rootcheck
Post #526: I just meant that is recommended to wipe if coming from 7. But of course, you can try installing without wiping before.
https://xiaomi.eu/community/threads/6-6-23.32335/page-27#post-302058
Just flash xiaomi.eu rom on your Mi Pad 2 via TWRP. You probably know that there's no MIUI 8 for Mi Pad / Mi Pad 2 so...
Last "dev" rom 6.5.26 (MIUI 7): https://www.androidfilehost.com/?fid=24566454284190003
TWRP recovery: https://www.androidfilehost.com/?fid=24421527759888024
As @ingbrzy...
Post #526: I just meant that is recommended to wipe if coming from 7. But of course, you can try installing without wiping before.
https://xiaomi.eu/community/threads/6-6-23.32335/page-27#post-302058
My Mi4 is not clicking xD. Anyway, try to remove the back cover and see if there is sth. Maybe is the back cover defective and you need to buy new back cover.