I don’t know if there is an all inclusive list for all major religions, but hebcal.com has a detailed calendar for Judaism. Not everything on the calendar requires Jews to take time off of work, so further research may be required to get the exact list that you’re looking for. It does give some explanation of each holiday on the site though.
Maybe it’s a skill issue, but this game was Star Wars Jedi Knight 2 for me. I think I played it on the second easiest difficulty. On higher difficulties, the enemies move much faster and do more damage, and you start to realize how inaccurate the guns are. On top of that, the weapons are projectile weapons, so you’re aiming inaccurate and slow projectiles at stormtroopers shuffling left and right rapidly. I think it’s much more fun to just play on the first or second difficulty.