Wow. Sounds so sad for everyone involved here, including you OP.
Her husband sounds like a very strong man and I really feel for the children both now and in the future.
While I know it must be devastating to see this dynamic on a daily basis, if you want this position to succeed OP, you must trudge on and focus on all the positives here.
The mother survived which sounds like a miracle in itself. While her quality of life has gone way down, she is alive and able to enjoy her children some of the time. And likewise for them as well.
Try to keep focusing on anything positive you can and keep everyone's spirits lifted.
There is nothing else within your power that you can do anyway, so it is best to just make lemonade right?
By the way, they are also blessed to have a caring and compassionate nanny like you in their lives. You sound like a true gem to me.
