Mode switch key mapping problem

Question

I searched a lot of wikis, forums but i didn't find out how to configure this.
I'm using the romanian keyboard layout, configured like this in xorg.conf:
Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbLayout" "ro"
EndSection
Alt_R / Alt Gr is by default mapped to switch modes. I managed to make the left Win Key change modes, by making a ~/.Xmodmap:
keycode 115 = ISO_Level3_Shift
Now both Alt_R and the left WinKey switch modes. I want to remove the mode switch from the right Alt, because i need it for other applications.
I tried putting remove / clear keycode 113 in .Xmodmap but it didn't work.
Also, why is arch/linux(?) using "ISO_Level3_Shift" instead of Mode_switch?
this is my output from xev:
for left winkey:
KeyRelease event, serial 31, synthetic NO, window 0x2000001,
root 0x155, subw 0x0, time 14283222, (43,85), root:(466,375),
state 0x90, keycode 115 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
XKeysymToKeycode returns keycode: 113
XLookupString gives 0 bytes:
XFilterEvent returns: False
alt gr:
KeyPress event, serial 31, synthetic NO, window 0x2000001,
root 0x155, subw 0x0, time 14283906, (43,85), root:(466,375),
state 0x10, keycode 113 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False

Answer 1

Solved it.
I tried to add Option "XKbOption" "compose:lwin" in xorg.conf but it didn't work.
Finally, I switched to US keyboard and defined the language specific characters using xmodmap. Could have done this in the first place but i thought there was a way to remove the Mode_switch from Alt Gr. It would have been more elegant.