Old Victorian Ceiling Falling, cracks, etc.

[Fluxburn]

I proceeded to paint my apartment, which seems to be from the 1940's or 1950's or earlier era. I am paiting entirely new color, as well as repairing cracks in walls as well as additional damage.

In a few particular areas, whatever the wall is made of(it has a layer that is affixed to the paint about 7mm thickness before you hit the actual wall) is coming apart from the underside of the wall. I proceeded to tear those parts of the wall, off the wall (it's not the actual wall, more like a stucco layer or whatever it is). I used the same crap to fill in holes and cracks in these large portions sometimes, 6x6 inch areas of the ceiling and walls. While it does the trick somewhat, not really because it does not look like the rest of the wall. The rest of the wall has more texture and it is hard to achieve this texture with this material, unless I can use an uneven tool or something.

What is the proper way to fix these areas, I don't want these areas to look half assed. Thank you.