Because of the rarity restriction in Pauper Commander, only uncommon Backgrounds can be your commander. Don’t forget that the common Backgrounds can still be used in the rest of your deck.
Casting either the creature or adventure from the command zone will increase commander tax. After resolving the adventure, it can be moved to exile or put back in the command zone. Casting the creature from exile does not apply commander tax.
An attraction deck must have 10 different cards, and Pauper Commander would require those cards to be commons. There are only 8 common attractions that don’t have the illegal acorn symbol, therefore Pauper Commander cannot have attraction decks.