QIf I summon Wind God with this follower's Fanfare ability, do both "At the start of your end phase" abilities trigger at the start of my end phase?

AYes. When you proceed to your end phase, all "At the start of your end phase" abilities are triggered and become pending. Then you can choose the order in which you resolve the pending abilities.

Note that even if you resolved the "return this card to its owner's hand" ability first, you would still resolve the "give each follower on your field +1 attack" ability.

QIf I summon Ancient Elf with this follower's Fanfare ability and return this follower to my hand with Ancient Elf's Fanfare ability, do I still have to return Ancient Elf to my hand at the start of my end phase?

AYes. Once this follower's Fanfare ability is resolved, Ancient Elf will have "At the start of your end phase, return this card to its owner's hand," which will remain valid even if this follower leaves the field.