1. What embarrassment and affection stats are for? Does they lock/unlock some scenes?
2. Does the gifts buffs summarize?
Embarrassment is mostly a debuff but does unlock some unique dialogue (currently only one line while she's in front of the gas station. More is planned.) Affection is mostly meant to unlock scenes down the line, currently it also has a flavor text in the gas station.
The gift buffs are all applied individually and can be used together. So if you have all 3 consoles Ellie does gain an extra 9 happiness every day.