iCloud Photos & Phone Storage Question

Alright, so I'm going to start by noting that I am something of a memory hoarder. I don't ever delete text messages and I take lots of candid photos of friends and family whenever I'm hanging out with them. Dating back to 2014 when I had a 64GB iPhone 6 Plus to yesterday when I retired my 256GB iPhone 8 Plus and upgraded to a 256GB iPhone 11 Pro, I have accrued just over 20,000 photos/videos on my Photos app.

This sum is in large part because I opted to transfer over all of my media from the iPhone 6 Plus to the iPhone 8 Plus when I upgraded back in 2017 and continued taking pictures, videos, and short films on it. Yesterday when I upgraded to the 11 Pro, my iPhone 8 was sitting at about 246/256GB. It was clear that if I wanted to continue having access to my photos, I was gonna need more memory. Enter iCloud Photos.

Now, when I look at my iPhone Storage on the iPhone 11 Pro, it gives me a few recommendations as to what I can do to help increase memory. One of the recommendations is "iCloud Photos" which claims will save me 156GB by automatically uploading and storing all of my photos on the cloud and let me access them on all of my devices (I also have a MacMini, iPad, and MacBook Pro--so great!) I went and sprung for the 2TB iCloud offering and have tried to initiate the process of getting my photos on iCloud. Last night, it got to around 22% before I went to bed, though I woke up to find that it had somehow stopped. Now, it either lags at 1% for a while before resetting to 0%, and it doesn't go past that.

I wonder what I'm doing wrong or what I can do to help ensure the process doesn't restart back to 0%. I'm also curious to know if, upon completion of the upload, will my phone really regain the 156 GB it is claiming I will save? I'm half-tempted to just wipe the new iPhone 11 Pro and start clean with it and have my iPhone 8 Plus serve as the keeper of all of those photos/videos, but I would REALLY prefer to have access to all of them from my 11 Pro and other devices without incurring storage loss to the device memory and rather have it eat away from the 2TB Plan I am now paying monthly for.

Sorry for the wordiness. I'm terrible and ramble and am just not one for being concise in general. Any help or advice on the subject would be very much appreciated.