1.) I'll agree that carrying a knife for self defense is not the best bet. I understand living in a not so great area, and there are shady people. For the most part if you stay clear of shady people and trouble they aren't likely to find you. This being said, I EDC two knives every day. Strictly for EDC purposes. But I know if something did come up, they would be there.
2.) Just because your friend has a $900 knife doesn't really mean you need one. They're nice and it's always great to have a nice knife, but you're young and I'm sure you'll get there someday. As long as you're happy and impressed with what you have, that's all that truly matters.
3.) It IS possible to have a knife that is good at all three things.
EDC - something that will handle and tackle all the tasks you need done, an EDC is not always light and thin. I EDC a ZT 0560 every day.
Survival - If the folder is tough, solid, and made to take hard use, it will work. I have absolutely no doubt in my mind that my folder(s) could and would handle this type of use.
Tactical - They have a certain look and are well known as self defense blades. Something that deploys quick and smooth is more ideal for this.
With all of this being said, I say get a Zero Tolerance knife. These fit the bill in all three departments.
Ones to look at:
ZT 0350 - This fits the liner lock you said you like but isn't really close to $300 and it sounds like you want something close to or at $300. It also isn't super large, which it sounds like you want a pocket monster.
ZT 0301 - Large, tough, ti frame lock, built like a tank, and you just can't beat it.
ZT 0550 - Large tough, manual, good steel, feels awesome in hand.
ZT 0560 - My personal favorite. Big, beautiful, not super heavy, heck of an EDC and would take anything I'd throw at it. Awesome blade steel and can be found here on the forums for a really good price.