I think you did a good job. As far as it being tight for the bolt head. What I would do is to cut a few groves into the bolt head with a hacksaw, to give some channels for the plastic to grip onto the head. Then I would heat the bolt head hot enough so it can partially melt the plastic. Then press the head into the plastic. I would try this on the first print to see how it goes before trying it on the better part. I had tried to do some plastic molding. I did not have a mold machine. The mold I made was for a dome for a light sensor. It was 50mm in diameter. I had virgin ground plastic that I placed in the mold then heated the mold in a toaster oven. When hot enough I pulled it out and put it on a drill press table and I used the chuck to press down on the top of the mold. I had a couple of holes in the mold that allowed the excess plastic to flow out. I held it until it was cool enough (but still hot) to remove the part. Pulling it off before it cooled completely allowed for easier extraction. I worked as an electronic designer and this was what I did to get some prototype parts. I'm retired now so I'm only working on hobby projects.

Good job!

Very well done

Where can I learn to make aluminium mold