question

It looks as though there are a few turns of usable thread left on the stud. A less invasive repair might be to get or make a female spacer (ideally from hexagonal bar), screw that on to the stub that remains, and then bolt the connection onto the top end of the spacer. No heat, no soldering, purely mechanical, easy to reverse.

Otherwise I think yr method 2 better, as method 1 likely to damage the soldered joint anyway. I think I would attempt it with the biggest bit on the end of my butane gas pencil soldering iron. You might also need to re-inforce the pcb track with e.g. copper braid to wherever it is connnected to.

Here is the replaced screw.

It was the first time I used a butane soldering iron, with a small bit. But it was outside with lots of light, and I didn't clearly see the flame, hence the small burn of the PCB itself. The metal parts are OK though, and I oriented the flame as to not heat other components. I worked on the other side of the PCB, but didn't take a picture of it...

The Multiplus works great now, already at full power (in and out of the battery), without any sign of increasing temperature near this port, as seen with a thermal camera.

Thanks @sharpener for the advices!