Time Machine runs as a low priority process by default, and this will cause it to be throttled whenever a higher priority process runs (and possibly to optimize energy usage on battery), hence the performance bursts.
You can disable throttling for Time Machine with:
sudo sysctl debug.lowpri_throttle_enabled=0
Keep in mind this might increase power usage on battery.
This setting will be lost on reboot. To make it permanent, create a launch daemon:
sudo nano /Library/LaunchDaemons/nothrottle.plist
Enter this text in the file:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>nothrottle</string>
<key>ProgramArguments</key>
<array>
<string>/usr/sbin/sysctl</string>
<string>debug.lowpri_throttle_enabled=0</string>
</array>
<key>RunAtLoad</key>
<true/>
</dict>
</plist>
Save it and exit nano (Press ctrl+X, then Y when asked to save changes)
Then enable the launch daemon:
sudo chown root /Library/LaunchDaemons/nothrottle.plist
sudo launchctl load /Library/LaunchDaemons/nothrottle.plist
Backups should now be performed at maximum performance.
In case you want to re-enable throttling, run:
sudo sysctl debug.lowpri_throttle_enabled=1
If you had enabled the launch daemon, run:
sudo launchctl unload /Library/LaunchDaemons/nothrottle.plist
Source
To answer your first question, you hold control and option together and then double click on the Time Capsule in Airport Utility. On the summary page you will see a bunch of stuff, but under where it says "Version: XXXXX" you will see that it shows MAC addresses for all of the interfaces 
Secondly, the TC by default restricts backups to only computers that have the password which can be set under the disk tab
I don't really understand your third question, but if it means what I think it does, you should connect over the LAN port because while using the internet jack does work, I found it causes instability within the network.
Best Answer
Answer to:
Time Capsule settings and user stored data are separate things. You can erase the hard drive and keep the settings, and reset the settings while keeping your data.