I will try my best to answer your queries
1. Yes it's normal.
2. Hard to see but again it's normal to have a dead pixel.
3. Yes you do need to have an antivirus for Windows. Free or paid which is your choice and only have one antivirus, having more than one will pose problems. Normally antiviruses today have a gaming mode feature meaning it won't interfere with your gaming by limiting the cpu usage, no popups, updating and etc. It'll still run in the background protecting the system but doesn't need user interaction.
4. Temp monitoring programs are useful but optimising/tune up programs are generally not essential. Must avoid registry cleaners completely.
5. If you try out software a lot then I suggest programs like RollBack RX that can undo changes to your system. Unfortunately Acronis's Try&Decide was removed from the 2015 version and also doesn't support GPT. I use backup to undo changes instead of using uninstalling programs like Revo Uninstaller.
6. You could check out in the Task Manager for seeing which applications are using a lot of resources like cpu usage and memory usage. Shut down file-sharing programs that may impact online gaming. Tweak the game settings and may have to bring some down like Anti-aliasing and Supersampling. However, you've got GeForce Experience therefore you can use that to optimise the games for you (the only downside, it works for some games).
7. You can use the
Windows 8 App Remover for that.