Don't worry, your loot will be safe.
Hearthfire's new houses aren't actually in place of any of the houses that were there in vanilla Skyrim - instead, three areas of the countryside are converted into potential building sites for Homesteads.
Your purchased houses and their contents, therefore, won't be altered.
Yes, you can.
Mods developed for the original Skyrim, with or without DLC, will work fine on the Legendary Edition, which is essentially the same thing, but provided as a complete set of the base game and all DLC (similar to a Game of the Year edition). Or:
Whatever mod requires Skyrim - with or without any additional DLC - will work with Skyrim Legendary ...
I've been assured that the vanilla console simply has no documented way to clear the console. At this point, I'm considering absence of evidence proof that this is so. That being said, I learned of a mod that does have a "clear" command that does exactly that.
More Informative Console for Skyrim SE. There is a lot you can do with that mod, but for me, all I ...