Regarding textfield issues, I forget, did we have a reproduction case?
preload="true" assets are loaded automatically at the beginning. If you set them not to preload, you can
Assets.loadBitmapData (etc) to load them later.
cache = true on by default when using
Assets.getBitmapData and other commands, but this can be set to false. You can also use
Assets.cache yourself, later, to clear references from the cache.
We use an Image, Canvas or ImageData object, depending on the use of a
BitmapData object, then also have a GL texture when you use WebGL rendering. You can test using only canvas rendering to not have GL textures, or
bitmapData.disposeImage () to discard the software surface once we have a GL texture ready instead. You might also try using your project without any sound, as perhaps something about the sound library inflates memory use for each sound.