The preterite is used because the sentence is narrating completed events in a match.
If you used the imperfect, it would sound more like background description or an ongoing situation rather than specific match events.
In Spanish, otro normally does not take an indefinite article before it.
So you say:
This is the normal pattern in Spanish:
Penalti is the standard adapted Spanish spelling of the football term penalty in Spain.
You may also see or hear:
In Spain, penalti is very normal and widely understood.
In this sentence, el marcador refers to the score or the scoreboard reading.
So it is not just the physical scoreboard in the stadium. It often means the actual match score, for example:
A close English translation here is simply the score.
Because seguir is a stem-changing verb.
In the preterite, the third-person forms change from e to i:
So siguió is the correct form, not seguió.
A nuestro favor means in our favour or favouring us.
It is a very common expression:
In this sentence, it means the score was still benefiting our team.
Yes, en nuestro favor is also possible in some contexts, but a nuestro favor is especially common with things like:
With sports scores, a nuestro favor sounds very natural.
You may also hear:
Because Spanish uses a possessive adjective here, not a subject pronoun.
So:
You would not say a nosotros favor.
Yes, it is understandable and natural enough, especially in sports narration, though some speakers might more commonly say things like:
Se mantuvo can sound slightly more explicit for remained, but siguió works well.