is the 2.7 GB the memory said at the bottom by C2? if so, remember this represents the layouts where, from the lyout view perspective, have the most memory usage, so if you have a dump layout where you put everything, that will say a very high value I guess.
Animations with 50+ frames, I wonder, are they nessecary, if you can get by with reducing them, it can help.
also
"optimize your pictures - 2^n x 2^n for your sprites."
well no, it is (2^n -2) as C2 will add 1 pixel all around each frame. but you can check if you used the crop option of the image editor for your assets (since you have quite a lot, it may make a big difference). also not using high quality downscaling but medium (you did not mention it, so I guess it is to medium, which is the default).
could we see one of the 2048x2048 spritesheet to have a better feeling of "can this be striped down with some other techniques" (like if you have 50 frames to represent a spinning ball around a ship, it will be better to make a separate ball, that will be spinning around the ship via events).