The question you need to ask yourself is "How would being ridiculously wide help the tree survive?" Generally speaking covering the ground with a forest of trees would outperform having only one tree.
I do have an idea about that. You mentioned the height limit for the trees. Higher the tree is more energy it requires to draw water and nutrients up from the soil. Until at some height from the roots the more or less constant force drawing the water is no longer sufficient and a tree cannot grow larger.
However there is a kind of plant called epiphyte that kind of gets around that limit. They draw their water and nutrients from the surface of another plant, not from the soil, so they do not care about height from the ground at all.
So what if we had a kind of plant that draw its water and moisture from its own top surface? (Autoepiphyte?) Its 100 meter limit would start counting from its own top, so it could feasibly, if slowly, grow two or three hundred meters high and leave all normal trees in its shadow.
It would of course have to be very wide to have enough top surface to gather enough water to water itself from the top. As in wide enough to build houses on top of. Which is kind of lucky for your needs. Additionally the width would allow the tree to survive high winds despite its height and make it nearly immune to forest fires. A fire wouldn't be able to penetrate deep enough to the massive trunk to cause lethal damage.
The top would be bowl shaped to gather rain with deeper depression for water storage in the middle. Although much of the water storage would be by saturating the trunk with water top down. The water pressure would add compression strength and make the tree even harder to burn. The central pond would still be vital for drought resistance. Branches would grow up from the rim of crown and sideways from the trunk where light is available.
The overall effect would be a nice little pond surrounded by trees with a view towering hundreds of meters above the lesser trees from the rim. Nice place to be, if you remember to build a safety fence or can fly.
The pond would also support other life. Cyanobacteria would fix nitrogen. Insects, frogs, and birds would bring other nutrients.