There's a couple of questions here.
First with para que. Once you hit the que, you have initiated a new clause and need a freshly conjugated verb. If you take out the que, then by virtue of having a verb after a preposition, an infinitive is the only option:
- Estudiaba para sacar notas buenas.
- Estudiaba para que me diese mi profesor buenas notas.
You can eschew the clausal form if the subject of the verb (that comes after the preposition, sacar in the previous example) is the same as the subject of the main clause:
- Estudiaba(yo) para sacar(yo) buenas notas.
- Estudiaba(yo) para que me diese(él) mi profesor buenas notas.
In your sentence, you can see there is a difference of subject, which normally causes the clausal form:
- Obama dijo que le había(Obama) dado más de un año al Congreso para que actuara(el Congreso).
The le is completely optional since the indirect object is explicitly stated (it's only obligatory if an explicitly stated indirect object is a personal pronoun like a mí).
The pluperfect había dado and había ocurrido is necessary because the year he gave happened prior to when he made the statement. After dijo que, the only verb forms generally allowed are pluperfect or antepreterite (happened before he said something), imperfect (happened simultaneously with when he said something), imperfect ir a or conditional (happened after he said something or is to happen). In more colloquial Spanish, present tense or even future is allowable if it is current with the moment in which the reporting of what he said happens (confused yet?).
