Large file size even after I delete all layers?

We can't know without seeing your document and understanding its structure by ways of screenshots of the layers palette. PS generates a lot of redundant rasterized data even with dynamic stuff like e.g. layer styles, especially when using maximum compatibility settings. Conversely, any layer mask or custom channel contributes extra pixel data that may be difficult to compress due to how it's used. Same for complex layer blending operations, smart objects, embedded 3D objects and what have you. at the same time, things like color modes influence file sizes - CMYK files almost always are more chunky than RGB. There's just an endless number of things that affect this stuff. With all that said, your file size is probably perfectly normal for what you want, so perhaps think about simply signing up to a more reliable cloud storage service with better quotas than CC... These days it's easy enough to get terabytes and terabytes for free just by signing up to a few different providers.

Mylenium