The stuff you're focusing on - basically manufacturing techniques - is a very small part of engineering in general. I didn't see any mention of CAD or FEA work, but even assuming you do know some of that or can access that type of learning you still are missing a lot of what makes an engineer an engineer.
The biggest difference I see between software developers and mechanical engineers is a way of thinking. I realize that sounds very woo, but it's very obvious to me and to other mechanical engineers I've spoken to.
For example, around my area there are schools that give out "Mechanical Engineering Technologist" degrees, which are quicker, less math intensive engineering degrees. Often times speaking to METs, I notice how they don't see connections between certain phenomenon or see why certain physical phenomenon happen in one circumstance but not another.
This isn't to discourage you. I think one very easy step you could do if you haven't already is pick up Fusion360 (it's free for hobbyists I believe) and try to simulate making a simple project. I would hesitate in calling this "mechanical engineering" but I think it would get you along in your goals.
Sorry for the long rambling message, the interplay between software and traditional engineering is something I think about quite a bit...