Food wise, some things have already been mentioned, like mussels with fries.
The beef stew is usually made with beer (in the good and decent places). God I miss this since living in the UK.
Another thing is vidée (or vol-au-vent), it's like a chicken/mushroom pie, but instead of having a lid of pastry on top, it's a little basket. My all time favorite, and the only thing I eat when going out for dinner, lol.
Obviously, get some Belgian chocolates, I prefer Leonidas as the best.
If you like TinTin, right in the middle of Brussels is an official store (one of the very very few official ones).
I remember a few doors down from TinTin store is a cookie store. Which in my opinion had amazing cookies, but I can't seem to find it on google maps either, so it might be gone
Drink tip I would suggest you try a "Kriek", it's a cherry beer, or is it sour cherry? I can never remember what the English word for them is (they look like cherries, but are much darker).
Panos is great, it's like UK Greggs, but better in my opinion, haha, sausage rolls are to die for! And the options on what you can have on a baguette ... (I haven't been home in 2 years, I really miss all this food, haha)
I lived on the other side of the country from where Ypres is, but been there once, there's the Flanders museum about the war, there's loads of cemeterys, we went to Tyne Cot, but it is quite out of the way of the city center, so would need transport or a bus.
There's the "Menenbrug" in the city center where they honor a soldier every night, it attracts loads of people, but also, now, I'm not sure if they are doing it for the public.