Is the tilde symbol okay to use in folder names? The filesystem is EXT4?
In general in Linux ~ undergoes tilde expansion, which is suppressed by quotes (or other means of escaping like \). Since you have spaces in file names, you will use quotes anyhow, I gather. And you should do this by default anyhow. So it should be ok. Same as here:
$ touch "~"
$ ls -l "~"
-rw-r----- 1 tomasz tomasz 0 Aug 6 18:12 '~'