I'm sure you can grow lots and lots of chains. Warming up is no problem, I have an old pot and let the wax harden in it after use.

Depends on various factors. But definitely >20 applications/chains. Yes, it can easily be reheated. I do it in a cheap slow cooker, which is much quicker than using water and a bag.

I haven't yet tested the product I recently bought. But according to information gleaned from the web, a metal container, an old saucepan or a multi-cooker, ideally with a temperature setting for the wax of between 90°C and 95°C, works very well. The problem with reusing wax is mainly the contamination that occurs with the chain over time each time it is reused.

The wax is enough for a lot of chains. I use an old camping pan to warm up the wax and leave it there for the next time. Warming up is no problem. I use a hotplate (Rotel U1113CH) for this.