Is this how one should use 'who', 'whoever', 'whom' and 'whomever'?

I know that 'whom' can be the object of a preposition, but since 'whom' is an object pronoun, and since only transitive verbs can receive an object(s) --- if this is wrong I'd appreciate it if you'd forgive me and correct me as I'm a learner of English --- is it correct that 'whom' and 'whomever' should only ever be used when one uses a transitive verb --- as only transitive verbs can receive an action(s)?

Additionally, is the converse true for 'who' and 'whoever' --- that is, that one is only ever to use the subject pronouns 'who' and 'whoever' when one uses an intransitive verb because intransitive verbs, though they perform actions, have no direct and or indirect object(s) like transitive verbs do?

Last thing: are actions and objects the same thing? If not could you please explain why; if so could you also please explain why?

Thanks in advance to everyone!

Yes. Only transitive verbs take a direct object. So you would use those pronouns this way:

Whom did you nominate for mayor? Hughes?
Yes, I nominated him.

An intransitive verb like sleep wouldn't work

You slept him? [wrong]
You slept whom? [wrong]

Note that some intransitive verbs can be used transitively. In the above case, sleep could be used that way informally or as part of technical jargon ("this cabin sleeps six"), but that is not a normal usage.