Is there a way to get a form into ODK collect without using Aggregate, perhaps adding it manually into ODK collect?
You can just copy your form into odk/forms directory on your device.
The second option is to use Google Drive - you can copy a form to your space on GD and then download it (you need to change your server in Settings - go to General Settings -> Server -> Type and select Google Drive, Google Sheets option. In the same page you have to select your google account (it's the second option). After that if you click Get Blank Form button from the main menu you should be able to see your space and your forms.
Regards,
Grzegorz