I don't think Lier was mentioned, and on the same train line is Turnhout. The latter is not as nice as, say, Leuven, but has an important Beguinage with a museum, a famous playing-card museum, a lovely cathedral with excellent wood carvings, and an art deco town hall.
Besides the doll museum, pretty Lier has a fine small art museum in/near the town hall. Try the local pastry specialty. There's an unusual clockmaker's life's work museum, with a massive multi-function clock at one end.
I went to Lille ("little Paris") for the major art museum. The train ride can get very long.
I'm also a big fan of Mechelen, Saturday market day. It's hard to find the Jewish Museum open, or the mansion-museum with a big Rick Wouters art collection. If you have enough time, Mechelen has an intriguing too-renovated "ghost" of a Beguinage. Very hard by public transportation, Fort Breendonk, a terrifying Nazi prison, full English audioguides. ( Google the Mechelen Trials.) The Mechelen town hall owns a lot of art, especially some gruesome "lives of the saints" panels that focus more than usual on their martyrdom.
Edit: I suggest you return to Antwerp for the museums you missed, like the Middelheim outdoor sculpture park, and the Cogels Osy Lei neighborhood. Watch for the massive KMSKA museum's reopening. The public park Rivierenhof is very nice on a warm day. Farther away, the Bokrijk open-air museum has a train station.
Postwar concrete Oosteende would be dull in October, but it still has a modern art museum, James Ensor's home and tomb, and a statue of Marvin Gaye at the piano in the Casino. Also good seafood. Coastal tram to the other shore towns.