I don’t understand why you want to change the port. There is no issue with using SSH to port forward to telnet port. In your client simply say that you want to forward the local port X to port 23 on the Linux server. Then tell your app to connect to port X on localhost.
But if you want to change the port then this is done in /etc/xined.d/telnet assuming Debian is using xinetd. Or if it’s using inetd then the port where telnetd listens is defined by /etc/inetd.conf
I also have a hard time beleiving there is no free SSH controls for Windows. There is multiple SSH libraries in the UNIX world, and I woul presume some of them is ported to Windows.. but Windows is not my field.