Avenues to collaborate with PHD students / professors while working
This is certainly field specific, but in general there are few straightforward fora where someone who is simply interested in research in general can collaborate with a PhD student or academic. Such collaborations occur and often the results are amazing, but they tend to arise more organically than a cold email.

Thus to answer your penultimate question: yes becoming an academic yourself is the best way to collaborate with academics and do academic research. As for finding a programme that is right for you, that's another kettle of fish and you should be looking for researchers who work in the area you wish to enter and consider them as possible supervisors: that's research for you to do.