What does Zach's powers expand to with those points spent on it?
With Level 3 in a skill means you're familiar with the subject, like a practiced hobby. Though unlike a skill trained everyday for use.
Level 3 in Offensives would Allow you to comfortably use your powers offensively, such as throwing Lightning, force-pushing people into the wall or force-choking them. You still can't do more fancy moves such as pulling the pin of a grenade off of them and such yet, and if you're under the effect of Fear you can still botch your rolls, but it's not as likely to cause your head to explode or something.
Utility for the force mainly include things such as Telekinesis, mind-reading and the likes. Mind Trick would also be a Utility skill but can specialize further into it, this is just a very broad term that allows you to do a bunch of things you see in the movie. You're no master, but you can kinda sorta do it.
Active Defense is the things such as unloading your opponant's gun, with just 1 level in it you could do it if it's not in a real fighting situation, and you're probably better off have it adds in to your dodge roll and perform somewhat more impressive dodges. Though smacking a grenade mid-air, throwing it back in the process would also benefits from such a skill. Enough skills in Active Defense and you'll be able to start blocking sub-sonic projectiles given they're big enough, such as arrows and bolts. Put enough in it and you might be able to block bullets with your weapons! This is not recommended, however, as one type of your weapon comes with a nuclear reactor and unless Light Sabers become a thing soon, modern bullet will chew through common metal used to make blades.