Install Linuxmint on your old computer. It will be much faster, cost = zero. I have 3 computers, one dual boots with win 8, one dual boots with win 10. I use Linux almost exclusively. No C D E ...Z drives. Graphically does everything. Updates are painless. Software is available for many apps, all free.
Finding the 'G spot' can be very tricky, or so I've been told. I use linux, don't use drive letters. Mac OS is derived from linux.
I tried "FreeFileSync". I didn't have much in the way of results. To do what you want try "file manager". It is already installed. If you open "file manager" then you should see your file server if it is attached. Moving/Copying files is very simple in "file manager". Just highlight the desired files and use "edit" and "copy to" or "move to". If you hit "F3" you can get a second window side by side. Then select your file server. One window is your source, the second is your destination. Permissions are important in linux, they should be in windows also but aren't. I don't think they will affect what you want to do.
If you want more help, please ask. The command line is not necessary for most normal operations.
I'm sorry you had such difficulty, but I'm glad you tried. Syncing to another computer can be challenging, especially to another OS. I don't generally sync to any other OS, but have done so occasionally. We have 5 computers all running linux and they all interact just fine.
Perhaps you could find an experienced linux user to help you. The things you mentioned are very simple in linux. For instance, there is no need to use the terminal to install an app. The software manager will do this very nicely.
Photo brings back many memories.
Not tortolla, Tortola. It is the main island in the BVI. Lived there for 10 years in the 70's & 80's.
It will cost you nothing to try GIMP. If you don't like it move on to something else.
Try Harbor Freight. Theirs will charge AAA, AA, C & D, and 9V but only cells designed to be recharged.
Download linux (it is free) and copy it to a thumb drive or DVD. Boot from the DVD/thumb drive and you can experience linux without making any changes to your computer. If you like it and have sufficient room on your hard drive, you can install it next to your existing OS and, when rebooting select, select either your original OS or linux. I recommend linuxmint, although there are many different versions to choose from.
If you know someone experienced in Linux ask them for help. I just googled "linux disk rescue" and found 10 different apps. I have used photorec personally. It will do the job. For those of you who don't use Linux, please don't disparage what you don't know.
You may have a "fake" SD card. A friend has purchased some from ebay. I have examined them and each has much less memory than what is advertised or shows in properties. They will act just like what you have described. A program called f3 will expose this problem.