Very sorry to hear of this.
For what's it worth, I have a certain nervousness around (Apple's) proprietary apps. In the case of my Photos, I keep all my pictures in a separate folder, and then named sub-folders within that - most often by year. Most photo manipulation I do by opening a specific image in Preview and working there. When I do choose to use Photos for other stuff, I do the work there and then Export the project out of it again. I keep nothing of value within Photos.
I backup my Pictures folder (or specific sub-folders when changed) manually to an external drive, as well as to a couple of Cloud accounts - though not iCloud, which really hasn't the free space for that.
And, for the most part, any pics I take on my iPhone I sync to an Cloud account (most often Dropbox) to access / edit later on my Mac. Meanwhile, via iPhone sync, I still have my pictures from my Mac (still in their sub-folders) available on my phone.