I do want you to try one possible fix. Power down the phone, by pressing and holding both the <down volume> and <power> buttons. Keep holding till the phone is completely shut down. Then press and hold the <power button> until you see the red "M" logo. Then release the power button and instead press and hold BOTH the <down volume> and <up volume> at the same time. Again, keep holding both until the phone's vibrator buzzes one short and one short and one long buzz.
This will put the phone into "Safe mode". If the screen and home buttons work, then there is the possibility to "fix" the default home key by going to <settings> <Manage Apps> and then scrolling to "Homescreen". Try clearing defaults first if you can. Then try the home button. If it works or it asks you to choose a default, you may be good to go. You may also wish to try Force Stop and Clear data, although Clear data will set you back to the default screen apps/widgets and wipe off the ones you have setup previously.
Then reboot and try it to see if you've fixed it. Let us know how it goes.~~