This is the same process I used to create the alias (on MacOS 10.13.6, a bit behind yours).

It was not creating the alias that required me to run the script. When I double click on my alias, the script opens in Text Editor instead of running in Terminal. Unlike a windows shortcut or Linux launcher, the alias doesn't have a property to let you specify the program you want to open the file in. In order to get the script to run in Terminal, I had to do the steps I described to define "open with" for the script file (not the alias file). This is the procedure where I had to actually run the script in order to specify the "open with" program. Once I had done that, I could double click on the script (or on the alias) and it would run in Terminal. I actually don't know if this now applies to all files on the system with the .sh extension, or just the one script file. The alias works in any location where it's located. I believe this is just a symbolic link like ln.

After having set the "open with" value for the script file, when I double click on the alias file, a terminal window opens, the script runs, and finishes, but I get the [Process completed] message and the Terminal sits there in a non-functional state without the window closing.

This is what I want, I just don't know why the Terminal window closes when the script is finished on your system and stays open on mine. I have run this script on both windows and linux for a long time and I have never seen that before.

LMHmedchem