1.- Which one should I choose? I'm already confused with so much info going around, I find myself now wandering this really simple questions, therefore, 80 or 160gb? HDD size doesn't matter. As
stated, go by the PS3 model number. If ya wanna play PS2 games you may wanna look into a used backwards-compatible PS3 with the Emotion Chip. CECHA or CECHB model.
2.- I'm gonna do it with firmware 3.55, right? Correct.
3.- Before or After jailbreaking, what do I need for actually playing the PS2 iso's?
Once again, I would suggest getting a PS3 with the emotion chip or; a CECHA or CECHB. If ya do that, Cobra USB would be able to play .iso from the HDD.
4.- Any extra comments? Research, research, research before making a decision. Good luck!