Which graphics card should I get? - 2

I have a HP Pavilion with a built in GeForce 9100, which can't even handle simple games like Minecraft. I want to eventually be able to run games like DayZ. I have the RAM (8gb), I just need a new graphics card, preferably under/around $150. I don't really know anything about graphics cards, so i'm asking for your help. Again I want to run games like DayZ on a semi-high graphics settings without spending too much money. Thanks!

BTW, here's a link that will give you all the specs of the PC

Minecrafts hostile mobs and cliffs?

When designing a shelter in Minecraft, I've noticed zombies, skeletons, and creepers will jump off certain heights of cliffs to get to me. My question is: how high does a cliff have to be for them not to jump? Or are they aggressive to the very end?

Minecraft launcher not finishing download?

[22:36:50 INFO]: Attempting to download C:\Users\user\AppData\Roaming\.minecraft\assets\objects\18\18ed93a18189c11bf6d6dd2d020b42782beb7189 for job 'Resources'… (try 1)
[22:36:50 WARN]: Had local file but it was the wrong size… Had 51757 but expected 69197

Minecraft mob spawning distance?

In minecraft you have to be 24 blocks i think away from mobs so they will spawn I built a mob spawn farm 21 blocks above me, so how far away do i need to be on ground level? How do i work it out?

Added (1). In other words, how do i tell how many blocks away i'm from something if it's above me?

I7 or i5 for a macbook air?

I'm getting a macbook air 13" for christmas but i'm not sure if i should get i7. I'm getting the 8GB and ill be playing ALOT of minecraft and some sims 4 and maybe more demanding games later on. I want it to be perfect because its alot of money and it will be my laptop for a few years so i need to get it right because i don't want to regret it.

Can the surface pro 3 run games?

I will be getting a surface pro 3 for school and i was wondering if the i5 surface pro 3 be able to run games like minecraft and the sims?