In the modern era, some Muslims have become very sensitive to the question of shirk by considering any number of physical objects to be shirk. This includes sacred objects, shrines, etc.

(This idea primarily comes from Wahhabism and Salafism, but some other Muslims have taken it on board too.)

Similarly, Wahhabism and Salafism reject most forms of intercession as shirk, whereas many Muslims before that accepted the idea of intercession.

The Qur'an itself does not state that the notion of sacred objects is shirk. Rather, shirk is when you directly worship beings other than Allah.

So, keeping an alam, in and of itself, is not shirk.

Possibly, some views are cultural. Since alams are most common historically in Iran and the Indian Subcontinent, it has been more common for Shia in other regions, where alams were not common, to criticize the practice. (That is, it was seen as being culturally different and hence suspicious - man is an enemy of what he does not know.)

On the flip side, some Muslims in the Subcontinent have felt cautious about the cultural influence of Hinduism, and so for this reason try to avoid physical objects in devotional practices. (We tend to be most cautious about the things we are closest to, which might be seen as a competitor.) Although I think this is less common.

A similar thing could be said for the Angel of Death: people are dying around the clock, and yet the Angel of Death is always on time!

Shaytan is a similar example - he can act on and be aware of many people at once, regardless of where they are located, without infringing on divinity.

Moving along from these morbid examples... My understanding is that once the soul leaves this world, it is not subject to the same restrictions of physical reality that we experience here (such as regarding space and time).

That could especially be said for those who have a high position near Allah, as well as other created beings which do not primarily exist on earth, such as archangels and the ruh.

Possibly they are able to "stretch" into various places at once while remaining in a place near Allah.

This is my understanding - Allah knows best.

In any case, this particular belief does not require ascribing them a divine attribute, although people may accept or reject the belief, or accept or reject the explanation.

It is a good question however!

Marriage is optional.

The short answer is, the Prophet (S) did it.

A slightly longer answer is: It is narrated that Imam 'Ali (A) was asked the meaning of the first prostration. He replied: It signifies saying O Allah, you created us from this – meaning the earth. The meaning of lifting the head is from it, You brought us forth. The meaning of the second prostration is to it You will return us, and the meaning of lifting your head again is and you will bring us forth from it again.

This is referring to the Qur'anic verse: ‘From it (the earth) We created you, to it We shall return you and from it We shall bring you forth once again’ (20:55).