Can I delete the old uploads and forms so I have more room again? If so, how do I do that?

If you delete a form you will clear all the files that were uploaded there, it means that you will have more available space, to delete a form simply go to My Forms page and click on the form you want to delete, once you've clicked on it go to the delete option on the top toolbar that will appear when clicking on the form: 

Once you have deleted the form go to the Trash folder and select the form, you need to purge it to make sure the files are deleted from our servers too: 

Hope this helps.