Hi Demonith,
Let’s see if we can help reduce the package size a bit. First, you will want to make sure you have set up your packaging to minimize the clutter as much as possible.
First, you will want to enable “Cook only maps” in the Project Settings>Packaging menu. Then make sure you have added only the maps you will have in your final game listed in the “List of maps to include in a packaged build” list below. It will start unpopulated with 0 elements, so if it’s empty, just hit the + and add the maps you want. Documentation Link. If that outright fails, then you may be experiencing some kind of bug and the support team will need to report it. If that is the case, then we’ll move this issue to the Answerhub, where it’s easier to get assistance with bugs.
Second, you don’t need to move the unused content to another project, but instead you can put it in your Developer folder instead of Content. You can locate that by clicking the “View Options” on your content browser and checking on “Show Developer Folder.” Any asset contained in a folder outside of the Content folder structure will be excluded from packaging.
Third, as said, you will want to bump up your computer’s power to meet the required system specs. I would suggest just getting more RAM if cost is an issue, because it is the least expensive upgrade that will have the biggest impact in build time. You can get 16 gigs of RAM for ~$55 or 8 gigs for ~$35 these days. You’ll feel the difference immediately.
Let me know if that helped you out!