All traits, psychological or otherwise are heritable. The hard question to answer is how predictive those inherited genetics are relative to other factors.

Yes, but tiny variations in phenotype will foster rather largely different outcomes. People forget that a lot of your genetic traits are there as potential, but not as fact. Its not even necessarily and upbringing thing. Epigenetica systems, multi generation genetic markings (like famine). Its very hard to say how a certain genetic trait becomes an observed psychological trait.