First off, disable the lagfix and see if you are still having problems. I enabled the lagfix on my phone and it became somewhat buggy, so I disabled it and everything is fine again.
If the phone is having FC's (forced closures) while syncing, disable auto sync one at a time for individual apps and see if it still happens. If it happens with every app, it's the auto sync. If it happens with certain apps, well, it's that app.
For someone with little or no experience in flashing custom ROMs, stay with the stock ROM. Do some reading on flashing, backing up the phone and installing CWM first. This
is a good thread to read.
If you decide to install the stock ROM with Kies, you will lose all your stuff anyways. The new ROM will wipe your phone when it gets installed.
There are 'no-wipe' versions of custom ROMs, but I never use them. This can only be good if you are not going from one version of Android to another, 2.2 to 2.2 or 2.2.1 to 2.2.1, but it's not the best way to do it.
Since you are on 2.2, if you install a custom ROM, it will be based on 2.2.1, so I would stay away from 'no-wipe' ROMs.
Kies can back-up all your music and contacts, but I do not know about the cover art.
You can install another launcher, like ADW.Launcher
, GO Launcher EX
, or LauncherPro
. If you use one of these, also install, Home Switcher for Froyo
as this will allow you to easily switch from one launcher to another. Do not uninstall the original launcher though.
If you are having positive results with another launcher then your problems are with TWLauncher. You can uninstall it and reinstall it. I have the APK for it if you need it.
Hope I've helped,