The -pa rule if it exists cannot have anything to do with Greek, because there are no such nouns what I know. Greek nouns ending in -a are feminine with one and one exception: those ending with -ma. They are neutral and therefore get masculine gender if borrowed to Spanish
Yes, la araña. In the word araña the stress is on the middle a, so the word does not start with a stressed a. Of course you remember the rules that tell you which syllable has the stress. For multi-syllable words without an accent mark, the stress falls on the second to last (penultimate) syllable if the word ends in a vowel or the consonants 'n' or 's'. Otherwise, the stress is on the final syllable. http://www.studyspanish.com/accents/rules.htm
Here is a website describing exceptions in 'Gender' Rule:
I hope it might it help you.
Yes, it is. I didn't think that one would count without that extra word in the sentence but I guess it counts. "Mine" and "My property" are basically the same thing, so that makes sense. You could add the word propiedad if you want to, but I think it would be "mi propiedad" instead of "mio propiedad".
One of the things I notice going through the reverse tree is that sometimes I see things like "El mapa es el mío". I understand the construction (literally it's something like "the map is the thing of mine"), but I was wondering if there's a specific context in which it's preferred, or if it's just a regionalism, etc.
Correct what I know. El mio is a possessive pronoun, see http://www.spanishdict.com/answers/100019/possessive-pronouns#.Vwi9I_AhWrU