Nathan, with all do respect, you need to reread your definition. Whom is used when it is the object of the verb. The pronoun may or may not be the subject of the sentence.
Websters defines it thusly:
Whom
objective case of
WHO
- —used as an interrogative or relative —used as object of a verb or a preceding preposition//to know for whom the bell tolls— John Donne— or less frequently as the object of a following preposition//the man whom you wrote to— though now often considered stilted especially as an interrogative and especially in oral use —occasionally used as predicate nominative with a copulative verb or as subject of a verb especially in the vicinity of a preposition or a verb of which it might mistakenly be considered the object.
Now lets review Col1:15-20:
15The Son is the image of the invisible God, the firstborn over all creation. 16For in
him all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities; all things have been created through
him and for
him.
17He is before all things, and in
him all things hold together. 18And
he is the head of the body, the church;
he is the beginning and the firstborn from among the dead, so that in everything
he might have the supremacy.
19For God was pleased to have all his fullness dwell in him, 20and through
him to reconcile to himself all things, whether things on earth or things in heaven,
by making peace through
his blood, shed on the cross.
In verses 15-18, "The Son" and all of the pronouns which follow referring to "the Son" are the subject, the nominative, and all the adjectival clauses are describing the subject, "the Son". The Father is not referenced in these verses. These are the verses that talk about "all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities; all things have been created through
him and for
him..." so the Father cannot be the creator in this passage.
The Father becomes the subject in 1:19-20, and is acting through "the Son", referenced by the pronoun, "him". All of these actions by the Father through the Son are redemptive in purpose and nature. Creation is not in view in these verses.
So all the bold font words refer to the Son alone as the nominative, and all of the italicized words are referring to the Father as the nominative, and the actions he accomplishes through the Son.
Nothing in this passage about the creation/creator is affected by Col 1:13-14 in the least. Verse 15 is a complete shift of focus, begun in 1:13-14, from the Father as the focus/nominative to the Son.
Lastly, and in recap, the sense in which you have applied the term "object" vs "subject" is incorrect, for as I demonstrated to you, to say whom is an object does not necessitate that it is not the subject. The pronoun Whom is the objective case of Who, which means that the use of whom is only proper when the action of the verb is received by the pronoun, or something is moving or given "to" the pronoun. It does not indicate if it is the subject or not, as Webster shows, it can be a predicate nominative, but may not be.
Again, the use of whom in 1:13-4 has zero bearing of the question of who is creator in 1:16. Verse 15 establishes "the Son" as the nominative/subject, and thereafter as the creator!
Doug