Are you remotely comfortable rooting and ROMing? If so, try a non-samsung build and see if it helps your issues. If you stick stable versions of things like CyanogenMod you can often end up with a much faster and more stable install than stock Samsung.
You may also try simply changing launchers before giving up. Try the Google now launcher and see if you have the same issues.
You may also try simply changing launchers before giving up. Try the Google now launcher and see if you have the same issues.