1) Race should have attribute differences. However it should not have all attribute differences, and arguably the attribute differences should be minor — a single +1 if the race has other notable benefits, like dragon breath or fey ancestry; possibly more for the bland human, though I might instead provide more skills or tools as it acts as more of a 'curious' race.
2) Culture should not be "from Waterdeep" or "from Icewind Dale" or whatever. It should be more generic and abstract, so that it can apply to basically any world setting. Rather, you're from a mercantile nation, or a culture developed under harsh climate conditions, or a warlike culture, or a crafting culture, etc. You're not from 'a place', but from 'a type of place'. The purpose of culture is to define a broad set of skills and behaviors.
For example, a mercantile nation may prize good negotiating skills, and thus a person from there is a good negotiator, whether he's a barbarian or a wizard or a halfling or an orc. A country with rigid formal structure may settle differences with duels, and thus everyone learns at least the basics of using a standard set of dueling weapons. Etc. This is the stuff you grew up learning and playing, and is also stuff that is likely to cause a culture clash when you go somewhere else. The good is that you gain bonuses. The bad is that those bonuses may cause problems for you if you use them somewhere else (ie: storytelling hooks or plot hooks).
These can be described using stereotypes (elf culture, or dwarf culture, or goblin culture, etc), but it would be better to describe the culture as its own thing, rather than who's associated with it. For example, if geblings are an insectile race that shares the mining and crafting descriptions you might in a standard setting associate with dwarfs, you don't want to describe them as having a 'dwarf' culture; it just doesn't make sense, and points to weaknesses in your worldbuilding. You instead want it to sound as natural as possible.
3) Background is personal, unlike culture. It's how you lived your life, the sort of people you associated with, the hobbies that you took a personal interest in. It's where you developed your life philosophies, interpersonal connections, and learned what you would live or die for.
I would consider Background the other section that could provide attribute points. This is, after all, what you personally focused on in your life, not the generic prevailing cultural preferences. This should have a higher attribute bonus than race, so I'd be inclined to put the +2 here.