The mood applies to the verb in a clause, not to a sentence.
English has a barely functional system of "moods", nearly all verbs are used in indicative (even in situations that plainly call for a subjunctive) And the imperative and subjunctive are identical in form to the infinitive.
If we weren't comparing English to Latin, "mood" would not be a big thing.
On the other hand, the matter of whether a sentence is declarative or interrogative is a structural and semantic question that affects the whole sentence, not just the verb form. A sentence can be made interogative by the use of particular words (what, why etc) or subject-verb inversion, or subject auxiliary inversion, or just intonation and context.
So it does not make sense to say "the sentence is indicative" But you can say "In this interogative sentence, the auxiliary verb is indicative.
Punctuation is a different thing again. Of course, there is no punctuation in the spoken language. In the written language, exclamation marks are used for a variety of purposes, only some of which are to mark exclamatory sentences. They are also used to indicate joy or surprise. "I'm pregnant!" is a perfectly good declarative sentence, that is marked with an exclamation mark to indicate emotion.