Game booster should not interfere with hacks, just antivirus could... disable it while injecting is recommended and in certain cases needed. Game booster anyway is useless, it can be useful to a legit player to close useless application that could be detected as hacks from server log, but for you it will NOT boost your game but instead make it slower. I think you shouldn't use it, but feel free to do what you want if you believe in magic.
1. Yes, you need to inject the .dll each time you run the game.1. Do I need to inject a hack each time I run the game?
2. Is it bad to inject hacks more than once? (Because I might have. ^.^;
3. Is there any way to "un-inject" hacks WITHOUT having to re-install CA?
Nexon detect the hacks very fast anyway, if you care about ban, don't hack, you will be banned there's no way to evade it at 100% if you hack everyday. But if you feel lucky, use the hack only few hours after release and then delete it.
2. You CAN'T inject more than 1 hack, they will not work.
3. They're automatically "un-injected" when engine.exe is closed. That's why you need to "re-inject" each time you run the game.
Few additional notes for you:
The lag could be caused from windows 8, try CA without any hack and check. Plus, not all hacks work on windows 8.