Ashley, just to clarify, there are no static frames that are larger than 1024x1024 (max size per frame 200kb), and all frame-by-frame animations are between 2 and 20 frames (max size per frame 50kb). I have looked into Spriter but it can't replicate the look of the complex animations I have hand drawn.
I don't think I'll understand this unless you show some examples of the types of animations you are using. But surely you have must hundreds or even thousands of animation frames in total?
Also when you are stating a size like 50kb, is that just the PNG filesize? As described by Memory usage, the correct calculation to determine the memory usage of a single image is W x H x 4, so a single 1024x1024 frame will use about 4mb of memory alone, regardless of the size of the image file.