'ee' will work, but nano is definitely easier, to install nano do 'pkg install nano'. (needs the pfsense box to have working internet access).
Also ronski you will have a much easier time using ssh instead of the console, then you can e.g. copy and paste stuff.
In the pfsense UI you will need to enable the sshd service, then download something like putty to use as ssh client and with that can login using the client on your windows desktop.
If you do ue 'ee' then when you done editing, press ctrl-c, it will show a command prompt, typing 'quit' will discard changes, typing 'exit' will preserve changes.
Strictly speaking only the second md99 line is needed in fstab, the first line is just a commented line used for showing descriptions of each column.