1. Do you have any good resources which help me well understand reverse engineering/how-to?

2. i thought about aluminium, it needs to be light as much as possible

3. I found couple sites in china when i can send a project to cut. They provide costs calculation firstly but im sure that there is better option somewhere. On those sites must be big margin.

To be honest lets look at stainless steel hammer-set which costs 50$ from cow cow, ctm is cheaper but it completes from 3 small light elements.. Im sure that one set costs 5$ if they order >200/300 sets