Sorry to hear about your troubles! I think most of the debug ideas I collected after reading your initial post were already taken up by Jake or Jason.
My first idea was that maybe D+ and D- were swapped. But I read you already tried it in both directions without success.
First off, while snapping off the on-board USB most of the time should not have any adverse effect, it is still a physical damage to the board. So far all the boards I used lost their USB at one point in time (some even deliberately), a certain amount of luck is always involved if it works afterwards. Therefore please check the solder pads of the late USB port for any shorts, I usually check all 4 signals against all the other 3 After wards you can check that there is still a contact from the USB breakout signals (VBUS, GND, D+ and D-) to the solder pads of the broken off USB connector. The pin ID does not play a role here, you just need those 4 mentioned.
If you wire up an external USB breakout board - and it is not as difficult as it seems, plus you can always source a bigger one if you are concerned about them being too tiny, there are old-fashioned USB-A and even bigger USB-C breakout which should work as well) - I'm mildly ashamed too of the soldering station I'm using - please check the voltages afterwards. If you do not have a battery connected, VBUS must read 5V, the 5V pad shall read ~4.2V, which comes from the on-board USB charger. If a battery is connected, the 5V pad reads the battery voltage, it should not be under 3.5V as a rule of thumb.
Once you can supply these readings we can see what can be the next step.