1 – it’s a pretty good choice, but not necessarily the “best” choice. Generally an alexandrite like Gentlelase is the best choice for people with light skin and dark hair, though a number of people on here had good results with the lightsheer (I haven’t used it myself), so I wouldn’t be too worried.
2 – usually 8 weeks is enough, but nothing wrong with waiting a little longer
3 – Those settings aren’t bad. In general, it’s not recommended to use below 25J. That being said, the beard hair tends to be denser and coarser so it’s ok to use a little lower settings for safety reasons, but the closer they are to 25, the better