It's best not to keep starting new topics with each new question you have (or have two separate topics for the same question) - you can just post all your questions in one thread/topic (you already have 7 different topics, all asking basically the same things).
In answer to your question: think about how much you will need for your trip rather than how much the IO will think you need - as each person they see will have different budgets and different amounts of money for their trip. How long do you think that $4,000 will last you? If you can show that the money you have will be enough for your personal spending during the trip, then you should be fine.
For example, if you're staying in a hotel that costs $300 a night, then your $4000 will only last you about 2 weeks, not even counting food, transport or spending money, but if you will be staying with someone in their house and not paying for your accommodation and much of your food, then over 2 months, $4,000 would give you $500 each week just for spending money.
What wouldn't work is turning up at the airport with only $500 to your name and expecting to stay in the UK for 2 months, because that $500 probably wouldn't last more than a week. The IO just wants to make sure that you won't run out of money before the 2 months is up... because if you run out of money, there might be the temptation to earn some more by working illegally, and the IO needs to believe that you won't have any reason to do this.
If you're worried about the amount, you can always ask your sponsor (your friend/boyfriend) to write a letter stating that he is willing to support you financially during your stay if you do run out of money.
