Happy hour/Dinner in Bruges

For what you have described, yes, it's easy. The train ride is less than two hours, probably closer to one than two. If you really want to splurge on an unforgettable meal: http://www.dekarmeliet.be/

The train (not Metro) leaves Brussel-Zuid (Brussels-Midi) twice an hour at xx:05 and xx:26 and takes 57 or 59 minutes to Brugge/Bruges.

Regarding a place for dinner, you didn't indicate how much you want to spend or what type of food you like. However, I would recommend Cambrinous, a beer brasserie with a beer menu that lists 400 beers and a food menu with delicious ions. I can recommend the mussels and the rabbit with prunes from personal experience.

Note that some of the famous attractions (indoors) in Bruges keep regular hours. Without meaning to insult, if you see Bruges as the movie, "In Bruges", hours don't matter! But if you want to see the chapels and the art, 3PM is too late to leave. I would even check to see how much of the outdoor Beguinage you can get into after 5 or 6 PM. On the other hand, Ghent/Gent has just as much to see outdoors (and for freeeee.) Would you consider leaving early for Bruges, and visiting Gent from 3 to 9 on the way back? Gent is the main stop, halfway there from Brussels.

favorite bar in Brugge: Café 't Brugs Beertje

Another vote for Ghent rather that Brugge. I far preferred Ghent.

Ghent is much more alive int the evening as well.

We based out of Gent and absolutely loved it. Easy day trip to Brugges and Brussels. And much less crowded and easy to navigate. And you definitely must eat waterzooi while there!