that has my cheat sheet for hooking up an htx-10
it might help to state your ‘goal’ for the radio.
are you trying to do ft-8 on 10m?
winlink on 10m?
allstarlink or echolink node?
i can answer the audio question.
when you unplug the microphone, the ‘speaker’ circuit is interupted.
(like cutting one of the speaker wires)
that is why there is no audio from the speaker when you unplug the microphone.
this was typical with ‘cb radios’ back in the day but is uncommon with ‘most’ radio gear today.
that is also why you can use that pin on the mic jack to supply the soundcard with rx audio instead of plugging in a wire to the back of the radio
there are a couple of threads here on the htx-10
take your time and glean what you can from them in order to get your solution.
good luck
kb0wlf