Non-responsive home button after changing lighting port

Inspect the home button and the connector if you haven’t already. Was the phone ever dropped in liquid?

As a student in electronics engineering, if there is a burnt smell on a PCB, that generally means there was a short circuit. In your case, it would be due to corrosion as a result of the water damage. More than likely, you are out of luck my guy. Unless you are a highly trained SMD/BGA soldering technician, it is almost impossible.

Burning smell means something burnt out, probably due to short circuit or faulty component, e.g. inductor, capacitor. You’ll have to dissassmble and look for anything that looks burnt out, look for cracks in components or brown marks or other discolouration.

If you’re lucky, whatever it was that shorted was not on the motherboard and so repairs could be relativley cheap. If home button not working is the only problem then perhaps swap out the home button for another and check. Repeat for taptic engine, lightning port, speaker and other components around that area of phone.

If your previous lightning port wasn’t working and installing new one caused a short there may be a problem on mainboard that’s causing a short in the lightning port circuit. Check the connector on motherboard and components around that area.

Does new lightning port still work after the short?