This rule:
1. Stressed as O
2. Unstressed & before the stress syllabus or in the begining of the word as A
3. In all unstressed ocasions as E.
most of all resembles the truth. But instead of "E" (point 3) I'd suggest you pronounce the sound like [ə], couse really it sounds neither as A nor as E.
So,
пАспорт = ['pas pərt]
пОрох = ['pɒ rəh]
порОг = [pʌ 'rɒk]
молокО = [mə lʌ 'kɒ].
Approximately this way.