Help with a sentence with pronouns.

The thing, situation or idea previously talked about.

The things in the sentence previously talked are football, windows and college.
I sense that football becomes the subject of the first sentence, and hence we choose football? is that what you are trying to imply?

If college was intended there would not need to be a sentence about windows and footballs. The football in the window is what makes this window different from other windows. If he liked windows it would be a plural, this is unlikely to be the only window he sees on the way to college, but quite likely only one has a football in it.

"If he liked windows it would be a plural"
It should have been window and not windows in the above post. I apologise.

"If college was intended there would not need to be a sentence about windows and footballs."
About this, consider the statements as a part of a paragraph.

"The football in the window is what makes this window different from other windows."
Exactly, what if he liked that specific window. It is very unliking but my point is what hidden rules did we use to identify that we ARE talking about the football and not the college or window (with the football in it).

It could refer to just the football or the feature of a window with a football in it.

If he'd just written, Dave was going to college. He saw it and he liked it.
then he'd be talking about college. He didn't just write that, he wrote a proceeding sentence about a window and a football, so that's what's referred to, either the football or the effect caused by the football.

Preceding direct object.

There is no way to be certain what the antecedent of "it" is. This a good example of poor English. The antecedent of a pronoun should always be made explicit to eliminate ambiguity.

On his way to college, Dave saw the football I kept in my window and liked it.

There is no ambiguity here because the object of the verb "saw" and the object of the verb "liked" are the same thing. It is the equivalent of saying "Dave saw and liked the football I kept in my window," which would have been the best way to say it.