Learn English – My father and the birthday/My father’s birthday and mine/My father’s and the birthday…something else

In one meaning of outstanding you could say it is describing things that stand out compared to other things.

As I read your examples, this is the meaning I get from them. This is sense 2 in the definition linked below.

When you use the phrase:

tracking the outstanding items

outstanding has a different meaning. Here outstanding means things that have not been completed or settled. See this definition outstanding sense 3.

I will finish the outstanding tasks next week.

"This is very worrying" means that something (usually a situation) is a worrying one, and is the correct one to use in this case.

"This is very worried" means that a particular thing is worried. You usually wouldn't use this, because the word "this" would usually refer to an inanimate object, and inanimate objects usually can't have feelings! Unless, of course, you are talking about your electronic pillow which can change mood depending on the weather. Or else it might just refer to non-human beings that don't have names or which aren't personified (such as animals which you don't know or aren't pets of anyone whom you know). Otherwise, one would usually use "he" or "she" to refer to the animal. (Though one would generally use "it" to refer to an unknown animal, not "this.")