There is not often much you can "do" in a practical sense, with #1 I would suggest that you just make sure they understand you are available if they need you but also drop in to see them, using the most minimal excuse you can, I do this with a friend as he lives on a main road so am passing regularily. Bake a cake or some such other excuse to go round they may not like asking for help but they will need it.
As for #2 it depends on whether they will talk to you openly about the behavour and their desire to move on, my experience is this can only be self motivated no matter your feelings on the matter.
I have two friends who have relationship problems at moment and as they are good friends I would like to help. One has been left by her husband and I want to be supportive and help but not intrude, what might be appropriate?
The other is fed up with her partner, he has a few behaviours she does not like and the relationship has been on the rocks for a while. Again, I want to help but don't know quite how to help her work it through. I think she is unsure about whether to stay or leave, or get him to leave I mean.
Any advice, they are both good friends and I feel a bit out of my depth!