I've had my indoor outdoor ficus for 24 years. It's now in the largest pot I could find that still fits through the sunroom door. My husband and I can barely drag it in and out anymore, as it's now quite heavy and about 10 feet tall. It loves to come outside in the summer and grows beautifully. It does require a lot of water in the summer heat, and I do soak it often to leach out the salts, which I don't do once its back inside for the winter. Around Oct 1, to avoid the first frost here in Nebraska, I prune and shape it, giving it a rounded appearance. I also treat it with systemic insect granules I dig into the soil, a few days prior. I use miracle grow diluted in water to feed it once a month. It looks nice with strings of lights and several pots of christmas cactus around the base for the holidays.
I often toss regular lawn fertilizer on mine, one with iron and sulfur when they are outside, and do not feed much after bringing them inside.
Like you, mine as so heavy I use a moving dolly.
I've also used mine as a Christmas tree many times in the past... Luscious in the summer, and being temperamental, when mine come in later in the fall, I wind up picking up the piles of leaves they shed.
It is a good idea to prune them heavily a couple weeks before bringing them in. They look so good by then, I have a hard time doing it till later when they look bad!!!!!