Glenn does not appear in the game thereafter, considering you did save Kid from the poison. Lynx can cross dimensions once he has serge's body. actually ,the dragon tear switched the minds of lynx and serge. when serge gets himself back, the dragon tear could not reproduce the original serge since he is a cat not a human now. the dt simply restores cell to their original form. however, switching serge from a cat to a human, not from a changed human to an normal human, proved too much for the dt, and it shattered. dark serge has the power to cross dimensions because dark serge is really serge believing he is lynx!
therefore serge has died twice, once by drowning, and once by murdering himself(out of body suicide basically). going to glenn's place in either dimension does nothing, it is just the 2 arguing boys and girl for the whole game in that house.