I can't answer them all but I'll try the ones I can as a solo/small instance
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I don't know about suggested, but I'm someone who likes to tinker and look behind the scenes a little so that's why I made my own instance, plus being in control of everything. Also having my name @va11halla.bar is pretty cool
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The account is gone, no migration. Part of why I made my own instance is because my old was deleted. Due to federation you can still find content you posted at least, assuming it was federated beforehand
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You'll have to federate everything yourself if its your own instance. The all tab takes into account the subscriptions of everyone on the instance, so you'll see a lot less if you have a lot less users on your instance. The local tab takes in to account communities on that instance only.