First, you have to get more free memory. You can't expect anything to improve until you've got at least 12GB free. Apple recommends that you keep at least 10% of your storage free. When the storage is too full, it interferes with even the most basic operations, and you may not even be able to delete pictures, then. You may need to remove some apps -- they're easy to get back.
You haven't let us in on really basic stuff, like how big is your Photos Library at iCloud.com? So I've had to try to figure it out.
I have 17K items that I keep in iCloud Photos which uses about 130 GB. You seem to have over 100000 items, so that should take maybe 800 GB. With "Optimize Storage" you can expect a fabulous saving of space, like even better than 90%. So it looks like you're right on.
If I were you, I would separate out the 10K or 20K of pictures to keep on the phone so they can be seen and shown, and keep the rest on a computer. That's what I meant when I said, "I have 17K items that I keep in iCloud Photos," because I have way more. I only put the ones that I might want to show others, my favorites, on my iPhone and iPad.
In any case, your phone isn't going to hold more stuff. You're going to have to figure out something.
