1. You will have the option when first starting a clean WebOS to restore from an existing profile.
2. It is much preferable to use OTA to update.
4. I do not recall off-hand and am currently running CM10, search this topic.
5. It is probably best to start over with mods (like turning on developer mode) and re-installing your preware patches. As far as I know, all should work on 4G TP.
6. The two internal antenna on the 4G TP work pretty well and I do not recommend attempting to add different antenna unless you really have severe problems.