Trying to complete as much on my own and ask mutliple questions in fewer posts:
1) Details of time spent out of the UK
- Am I correct to include holidays to Spain (honeymoon, etc.) and back home in the US?
- Am I correct to include business travel (Denmark)
Include every single trip you have made outside the UK since you moved here.
2) Your family or friends
- How many people/how far back do I need to put down in terms of family?
- Is it just immediate family (parents and brother)?
- How many friends do I need to put down?
You put every single person you can think of, starting with immediate family, then extended family, then friends.
- I'm guessing this is because I answered that I have been back to the States with my wife on holiday to see friends and family
No, you are asked this because it is a required question on every visa application made within the UK. You will be asked it on your next application as well.
They need to see whether, if your visa falls for refusal, you have a support system to go back to in the US... or whether they need to consider allowing you to stay in the UK under Article 8: Right to Family Life in the UK... because if you were to be sent back to the US, your life would be in danger (i.e. you would have nowhere to go, no family or friends to help you, no financial support etc.)
So, when it asks you whether or not you could live with your spouse in your home country, it's also for the same reason.
They need to see whether, if you had to return to the US, your life would be in danger due to things like:
- war
- terrorism
- famine
- natural disasters
Or, if your family would be torn apart because, for example, your spouse is banned from entering the US and will never ever qualify for a visa to move there with you