How to avoid report of unsuitable sketch names?
That message is actually a hang-over from when the IDE was Processing.  The name of a file had to match the name of the Java class within that file, and there are strict rules about what can be in a Java class name.

They just basically haven't got around to deleting that piece of ancient code yet.

So you have 3 options:


Rename all the folders and files.
Edit the IDE's source code to delete that old code
Use a different IDE.


The first option can be long winded if you don't know how to do good scripting, as you have found out.

The second option requires knowledge of Java coding.

So that leaves the third option.  Now, I'm going to be shamelessly advertising my own work here ;)  Why not try a better IDE?  Such as the popular and powerful UECIDE (yes, written by me). It's based on the Arduino IDE, so it will mostly be familiar to you, but the whole of the insides have been ripped out and re-written.  If you're feeling brave you might want to give the beta version a go - it has some really really cool features not found in any other IDE in the history of mankind.