So I was following this guide of creating a low poly person and rigging it, and as you can see he created a person from multiple cubes and spheres and connected them to one rig manually, by selecting each object and connecting it to a proper bone. That works beautifully and it's simple, intuitive, and fast to me.
Now I wanted to import my model with working rig to Unity, and he also has this guide. The first problem is that he uses a model that is a single object, so I just use Ctrl + J to merge all cubes and spheres into one object, but it breaks the rig completely. Here he uses automatic weights and weight paint, and both of these work terribly in my case. I wouldn't have such a big issue with facts like the forearm actually moving some bits of my legs as well if the weight paint tool wasn't so painful to use for me. I struggle so much to remove every bit of paint anywhere besides where it should be and, even if I succeed, I can never get it to work as it used to while using the first method (like forearm scaling down and leaving the bone while rotating for whatever reason).
Is there any way to somehow merge these objects and keep the skeleton working? I do realize that the rig breaks because references break when I merge the objects, but there's a couple of reasons why I wanted it to be a single object, like changing the center of the whole object to the bottom and make it work so I can animate it with Unity.