The fact that Richard totally gives up on life immediately after he accidently brings himself back to 1980 really is ridiculous not only from a character development/story writing perspective, but the fact that Christopher Reeve faced much larger and tougher situations/obstacles in his own life and the man never gave up and kept on fighting to the end.
The fact that the Richard Collier character gives up so easily due to being in a situation that really is not one of true hardship really makes the story seem lazy and flimsy.
I was a bit confused. Did he wake up in her room from the past, then run back to his empty room? Then he spent a week in there trying to get back to her in the past and didn't eat, getting sick. Maybe he was in some kind of semi-trance-like state stuck somewhere in between then and now, another dimension, where he couldn't care for himself.
When Richard went to speak with his old professor about whether or not time travel was possible, the professor said that he himself had tried it once in Venice and that he would never attempt it again because of how draining it was. And the professor said he'd never even fully achieved it! So I think that was the setup for what ultimately happens to Richard, who did manage to achieve it. It drained the life out of him. Ultimately they had to end the film somehow! I personally love the way this movie ends.
As a side note, I just watched a new Australian time travel movie last set in my home town called Time Addicts. It was quite amusing with some interesting twists! The humour is not for everyone but being Aussie I connected with it.