In regards to camera problem
Ok, so i'm in exactly the same situation you are in as the recording feature of the stock camera app or any app failed to work for me (froze and crashed app). So far I have found two fixes, the first one thanks to a user called "RambJoe", so thank him if it works (it didn't work for me
1. Install/Open a file explorer on your device (I used ESFileExplorer)
2.Enable "Root Explorer" (Under Menu>Tools>Scroll to bottom on ES)
3.Navigate to system/etc/init.d/80cfw (This file seems to be missing on my phone, and I have found other people who have not got it as well. I believe it is because this guide isn't compatible with the International version of the SII i9100, so if you do not have it, skip to Fix 2)
4.Change the permission of the 80cfw file to rwx r-x r-x (Select the file, tap on "More" and scroll down to "Properties" and change the permissions from there)
5. Save and reboot, that should do the trick!
The next fix requires you to have Titanium Backup (FREE) to be installed or another such app that can delete/modify system apps. You can thank me for this one
1. Download this apk *DO NOT INSTALL YET* - http://forum.xda-developers.com/show....php?t=2340858
(Thanks nexūs0 for upload)
2. Open up Titanium and back up, then delete your stock Gallery app
3.Find and install the apk you downloaded in step one
4.Open up the Gallery app and you should find the camer ON THE GALLERY APP ONLY working correctly (it did for me, anyway). The other camera apps still do not work
Don't forget to tell me if this helped you and feel free to PM me if you need assistance!