You seem to have a pretty good understanding of the tenses and voice now, below are some comments I had, and where I haven't commented I think your explanations are fine.
1) “Madonna’s body remains in remarkable shape for 50”. (Present simple active voice). This use of the present simple tense here is to say that the action is not only happening now but happens but occurred from the past to the present.
The reasoning you use sounds like you might be confusing it with present perfect, which is the tense where a connection from past to present is important.
Present simple tends to speak about general things such as habit or the state of something or someone.
He is a Doctor.
He plays tennis.
He is athletic.
The use of Present simple tense here is to state that the action is happening at the present time.
That is actually a better explanation for present continuous. Present simple rarely means something is happening
at the present time, and you might note that you needed to use present continuous to describe that.
Present simple in this case is just describing a current truth. He is seen in that photo shoot, but the shoot or the seeing doesn't have to be happening at the present time, it just has to be true at the present.
This sentence is in the passive voice because the subject which is ‘The singer’ does not do anything but is having something done to her.
More specifically, the subject of the verb is left out. "He is seen" doesn't need to say who sees.
4) “Madonna has spent most of her time living in New York”. ( Present perfect simple). The use of this tense here is to state that the action began in the past and continues to the future.
Continues to the present
. Present perfect has a connection to the present
5) “He has been filming his upcoming Sherlock Holmes movie”.( Present perfect continuous). The use of this tense here is to state that the action is in progress and not completed.
Well present continuous can be an action in progress that is not completed as well, present perfect continuous is generally used to describe events that were ongoing from the past till the present but they do not need to be incomplete. For example:
I think he is finished the project, he has been working on it all week.