Will this suffice as evidence of ties to the US?

Hi everyone, I posted this a few days ago and I have some edits and further questions - I apologize if I should have updated the old thread rather than make a new one, but I wanted to make sure this was seen. 

"I am American (29F) and have been with my English boyfriend (23M) for two years now, one of them long distance. We met in Australia while on Working Holiday visas. He has visited me twice in the US in the past year for 6 weeks each time and had no trouble getting through border security. I entered the UK in the EU line with him after leaving Australia and we were questioned at Heathrow but nothing too intense, they just wanted to know if I had a return ticket and how much money I had available.


I'm visiting him for 3 weeks in May and will be staying with him and his family in various locations (Sheffield, Birmingham, London etc). I will have a printed out itinerary for the visit. I have a return ticket booked as well as travel insurance.

My concern is that I have just been terminated from my job (for asking for time off for this trip!!). I'm very worried that I will be denied entry at Gatwick for being unable to show strong ties to the USA, as I currently live with my parents (hard to get back on my feet after backpacking), hence I have no lease, while being recently unemployed. I am concerned that they will think I quit my job to move to the UK illegally if I tell them I am recently unemployed. I work in marketing and have an MA for what its worth, not waitressing or anything easily transferable that could rouse the IO's suspicions that I could work under the table.
 
I work very very part time for my father's business as a marketing assistant, but I don't have any evidence of pay deposits. Would a letter from him saying I am employed by his business help or would they disregard that, since he is my dad and I don't have pay stubs? He works on occasion with an events company and he is learning web development and freelancing at that. He lives with his mother.

I will have a few thousand dollars in my checking account and I will also bring a few hundred in cash. What are the odds of me being given a hard time and denied entry?"

Ok so the updates:

• I have three doctor's appointments scheduled for the end of May and the beginning of June, and I have printed appointment confirmations and a signed form from the doctor stating I have an appointment on May 28th. So I will have 3 appointment confirmation letters to bring.
  
• I have a save-the-date card for my cousin's wedding in Maine in July
  
• I have a printed itinerary of what I want to do in London
  
• I have a printed itinerary of everything I want to see and do in the UK for the entire trip
• I have purchased the Lonely Planet England book and will have post it notes on the pages of things I am interested in doing.
• I will have about $2000 in my checking account and will also bring a couple hundred GBP in my wallet.
• I have a return flight and will print the confirmation.

So, my questions are:
A) Does all that seem like adequate proof that I will be returning to the US when the 3 weeks is up?
B) Should I write "none" or "unemployed" on my landing card, or is it ok for me to write that my profession is Marketing? I mean it says Occupation/Profession so that is truthful.

Thank you!!!!

As you're only coming for 3 weeks, there shouldn't be much cause for concern.

I would bring with you:

- your return ticket
- your bank statements showing how much money you have for the trip
- a letter from your parents stating that you live with them (if you pay them rent they can state this too)
- a letter from your father stating that you work for him
- print outs of your doctor's appointment dates
- the save the date/invitation to your cousin's wedding
- your printed London and UK itineraries

If you're bringing the Lonely Planet guide with you, you can always show it as extra if they ask (if you bring it in your hand luggage)

So, my questions are:
A) Does all that seem like adequate proof that I will be returning to the US when the 3 weeks is up?

I would think so - it's the best you can do anyway)

B) Should I write "none" or "unemployed" on my landing card, or is it ok for me to write that my profession is Marketing? I mean it says Occupation/Profession so that is truthful.

I would probably put both, for example "Marketing (between jobs)"