"He heard a person in his house."
Translation:Han hørte en person i sit hus.
Right, I was interpreting it as the house of the person heard, not the person doing the hearing. I would have thought it referred to the person most recently referred to not the subject. In other words, I was thinking that "Han hørte en person i hans hus" would mean "Han hørte en person i personens hus."
Yes, most verbs in the past tense are either "-te" or "-(e)de" (with "-t" and "-(e)t" past participles respectively), however there are some verbs that conjugate the past tense differently depending on meaning, and some which could be both, but these are of a tiny minority. There are of course irregular verbs, but most of these will have to be remembered on a case-by-case basis.