So those are two sliders that quite frankly.....is personal taste.
If you like injuries at 50...by all means go for it.....but you will have a league full of 2nd stringers soon enough in my testing. 23 still is a great sweet spot for played games and 52 when you advance your week.
As far as the fumble slider. Yes, the lower the value the more fumbles...the higher the less. Your choice. I like the risk of fumbles and I did not see nearly enough at 48 after extensive testing. You must remember to cover up with R1 and especially if you are a QB getting taken down.