The best date atmosphere kosher restaurant in Baltimore is Umami, hands down, and the food is amazing. They even have a "Revolution Diet" section on the menu for super healthy food served to you in your own bamboo steamer.
Downtown, there are tons of museums. The best is the Science Center; the worst is the American Visionary Art Museum. Anything else depends on your taste.
Also downtown, you can see an Orioles game if you and the guy are into that. I think it's a fun date even if you don't care about sports.
The Inner Harbor has duck boats you can take, and there's a kosher Rita's ice cream there (terrible service, but whatever).
Reisterstown Road has a bowling alley. I love bowling on a date because it's active. They also have pool, air hockey, and arcade games.
The zoo and the aquarium are classic date spots; I don't like them, but others do.
If you've had a few dates already, take him to the Wellwood playground! I like to see if a guy can relax and be a kid. Climb up and go down the slide, or just sit on the swings and talk. It's a remarkably calming and chilled-out atmosphere.
In the summer, you can go to the Maryland State Fair. I was once at the state fair and I ran into my friend's sister on a first date. I thought they looked like they were having a good time, and I guess they were-- they are now married with three kids!
I also recommend walking around the Quarry. It's got gorgeous scenery and nice walking paths, plus nearby there's a Starbucks and a Coldstone Creamery.