With Windbg setup on either computer, each one indicates a connection to COM2 but both freeze, allowing no input, while displaying something like 'waiting to reconnect'.
what do you mean by this ?

you do not think that windbg on host will be talking to windbg in guest(target) ? do you ??

it is one way traffic the guest talks to the windbg running in host about all the events that happen in the guest(target) machine

the windbg in host listens and breaks when appropriate for the human on the host to interpret and handle the event

stop take a breath throw away all the wires and create a vm first get your first break take few baby steps in and out of the code
force forget sice it is and old extinct dinosaur get your feet wet first no point talking 10 things and not doing even one