"4GB RAM with 3.73GB usable" means that your main system RAM is shared to your laptop iGPU.
Nothing to worry. Because integrated GPU doesn't have its own memory, that's why it consumes 270MB of system memory for shared VRAM.
You can change the shared amount of memory in your laptop BIOS if its supported. Just look for "MAX DVMT shared memory", "VGA Aperture size", "DVMT MEM", or just simply any shared video memory option. But sometimes iGPU shared memory are controlled by GPU driver itself, its called "dynamic VRAM" (I think, If I'm not wrong).
For your storage problem, you can buy external HDD for cheap and move any of your unimportant data into it (like: old photos, old documents, backups).