Also, unless you have a very old PC with a regular serial port, you need a
USB-to-RS232 adaptor, plus special drivers installed, to connect to the MAX. So, what
are you using here?
To give the OP the benefit of doubt (yes, dangerous...), he may have a serial card in his PC. This is common in laboratory situations where one needs to interface their new PC with legacy equipment. (It's also common for lab PCs to also include floppy drives, as some older test equipment (like our very reliable Textronix bench scopes) save data to floppies only.)
But, your other questions (that I snipped for brevity) are valid.