Nicotine has never been addictive to me, whatsoever, no matter how many years I've smoked or how many I smoke a day.
Ehm, they probably mean well but don't listen to them. R1GL does not support negative gl_mode values. So open your config or autoexec and just change it to something else, eg. gl_mode "6" (as long as it's positive). That should solve the problem.
DING DING DING!! Winnar winnar, chicken dinnar!!!
That sure was a weird fullscreen issue.