iCloud Photo Library for multiple libraries?

Hello! I have a few questions about working with iCloud Photo Libraries that I haven't been able to find the answers to, so I hope someone can help me!

I like to organize my photos by year and have separate libraries for each year. All of my libraries (2012-2016) are backed up in multiple places. It wasn't until last year (2016) when I started using iCloud Photo Library to automatically upload and store my entire library in iCloud to access photos from all of my devices. I have the preference set to download the originals to my Mac.

It was just last week when I had a moment to split up my 2016 photos from the first few months of 2017. I have set my new Family Photos 2017 Photos Library as my system library and have moved my Family Photos 2016 Library to an EHD which is also backed up offsite (Backblaze).

My issue is this: I don't want my 2016 photos in iCloud Photo Library anymore and it is my understanding that if I turn on iCloud Photo Library and set the preference to "Download Originals to this Mac" in my 2017 Library, it will add all of those photos from 2016 back into my 2017 library, and I don't want this. I just want to be able have my 2017 photos in iCloud.

Is there a way around this? Am I able to delete the 2016 photos from iCloud Photo Library? If so, will the photo still be in my Family Photos 2016 Library when I open that library again (as a reminder, the 2016 library is saved on an EHD and backed up to Backblaze).

I really need to have access to my full-resolution photos on my iPhone (128GB) and recently I have been getting a low storage warning. I have no need to access my 2016 high-res photos on my iPhone anymore and really only need to store my 2017 ones in iCloud.

Any help you can provide will be greatly appreciated.

Thank you!

Kelly Sill