If this monitor
is the one you are using then:
1. No. The max resolution per the tech specs is 1280x1024
2. If you're using KDE, right click on a blank area of your desktop, then Configure Desktop > Display > Size & Orientation
3. Higher refresh rates are easier on your eyes; I'd suggest using 75Hz as the minimum. Trying to force the monitor to use a faster refresh rate than it's built for can damage it
4. Most likely, if would just stop working. I don't think it would act funny for 2 or 3 weeks and then go down.
I would ask if the system really truly is using 1400x1050. If you previously were using a lower resolution, say, 1024x768 but now are using 1280x1024, the difference can seem significant. In any event, under no circumstances would I recommend trying to force a monitor to use a resolution that is higher than what the manufacturer has specified. Good luck with it and Welcome to LQ -- J.W.