Recommendations for newbie on LR photo saving location

Hello all, I've been using Lightroom on a Mac at a limited capacity (only to make basic adjustments to brightness, colour, shadows etc.) for a number of years. I'm an amateur and I've never had training on how to use it and found hour-long youtube videos a little hard to follow (as the versions and terminology always appear a little different to what I see on my screen). I only use it out of my own interest in my personal time.

Anyway - my photo library/catalogue is now bloated to 1TB+ and it's really eating into my computer hard drive space. May I seek some advice from the experienced users as to:

1. should I ask LR to store the original photos on an external harddrive? I suppose this means I will need to plug in that particular external harddrive whenever I want to work on Lighroom. As I'm running out of space on my internal harddrive, I've just asked it to migrate it to my external harddrive (as a stop-gap) which I've been using for long term storage of images. Not sure if this is a good idea - but I'll need time to acquire another harddrive (if necessary) for storage of LR catalogue/library. 

2. I actually organise my photos from different cameras into a folder system of my own saved into a few harddrives (in duplicate) by year, and then a folder starting with the YYYY-MM-DD which stores my original RAW and JPEGS and an "edit" subfolder within each of the folders to save processed images as JPEGs. What I've just realised is that whenever I add photos to the albums in LR, it is making a copy of the originals, which means it is duplicating all of the images that I add to LR. I've amassed upwards of 15TB of photos (perhaps not a lot for some of you), and while I do not intend to add them all to LR for processing, the duplication will only be an increasing issue as time goes on. Is there anything I can do to avoid this while keeping my existing folder system which I keep for all photos?

3. As the storage which comes with the basic LR CC is only a number of GB, there is no way that the library/catalogue will fully upload to the cloud and I've paused sync-ing the day I subscribed to LR. Surely most people will have more images than what is included in the basic subscription. Am I using (I guess I'm not actually even "using" the cloud feature) this wrong? 

Thank you very much.