decidessi io non rimarrei
It should be "se decidessi io"= if it were up to me, if it was my choice I wouldn't stay
resta cieco chi non ne ha
whoever has no fault goes blind/is blind
the phrase sounds a bit odd, it could be "you paid the consequences, you paid the price for what once happened" (her theft perhaps)
fossi in me berrei ma ahi
It could mean "if i were in my shoes, if i were me".
Usually it is used with other subjects: se fossi in te/lei/loro berrei ma ahi= if i were in your/her/their shoes I'd drink but alas...
"Essere in se/fuori di se" can also mean "be in your right mind, behave normally, be fine/ be out of your mind or be beside yourself -with anger usually-.
"-Please tell me you're going to appeal to my humanity..."
"-Actually, I'm planning to threaten you."
"Well, if you'll excuse me, I have work to do. Evil plots don't just make themselves, you know!"