Welcome to BLF, eliasklk_04! 
The led you are using seems to be a genuine XHP70.2.
If you paint the internal area silver and zoom the flashlight it will project some rings and artifacts in the beam. It may increase the lumen output but most prefer a pitch black interior for an artifact free beam.
The four R750 resistors are the sense resistors that limit the output current. They will get hot because all the current passes through them. If you want to increase the current you need to replace the resistors with lower values or place some new resistors on them. These resistors are needed and can be found on every buck and boost driver to limit the output current.