I think everyone is correct that the 4th Ideal is something along the lines "I will protect those that I can, and accept that I can't save everyone."
The only additional insight I have to add support to this is that Kaladin repeatedly remembers his father wanted him to grow emotional calluses, for this very reason, and he was never able to do so. It's been mentioned and referenced far too many times to not be significant. Also, when trying to leave Shadesmar, Sly wanted him to say The Words. However, at this point, he was still too freshly conflicted that he was unable to stop his Parshmen friends and Wall Guard friends from killing each other.
I'm a bit more uncertain about the 5th Ideal but I believe it's going to be something like "I will not heedlessly endanger my life to protect others." I only have a few details to support this and they all involve the differences between the orders. The first is Syl commenting she's not a Cryptic and second is telling Kaladin he's no Skybreaker. The final, and maybe most significant, is the prelude the tWoK. Kelek mentions that Talenel has a habit of basically choosing suicide missions in his defensive positions. That might be another difference between orders. The Stonewards might "encourage" acts of self-sacrifice while the Windrunners don't. While dying in battle often inevitable, to rush in headless of the obvious consequences would be against the ideal.