Well I am certainly a person who needs time and space for myself, I just told my husband that I wanted each Sunday to myself (sometimes its a 4 hour chunk of time, sometimes I take all day and night - usually it is to just do my own thing in my house. He will go out, or use the computer room if I am not, or go to his room to watch movies or play games depending on what part of the house I want to be in.) Sometimes I want even more more time to myself and so we have a second day a week scheduled to do our own things - don't often use it but it's nice to know that it's not a surprise for him if I want more down time.
Hmm sheesh - I don't remember exactly what I said, since we hashed this out 6 years or so ago, but it was along the lines of, I love you, but I need time and space to myself to be happy and keep my stress levels down. I need time to be able to do my hobbies, or to feel like I can watch movies you don't want to see, or listen to music you don't like without it having to be "a big deal" to ask for it, so I am going to schedule this regular time for myself so I know I can do that. Doing so will make sure we co-exist peacefully the rest of the time because I wont be walking around irritated and tense that I am not getting my needs met.
More it was probably like - dude, listen, I need to relax on Sundays or I'll stab you, so I'm taking that day for myself or you'll have a high strung tense person to deal with...and all the other stuff was discussed over time.
Can the king bed be moved into their room?
You have every right to ask for some personal space back if you need quiet and calm to write, that would probably be a firm boundary I'd insist on. If you need that to be happy, then I'd say "I need this to be happy/keep my sanity, so I'd appreciate if you two accepted that and didn't make a big deal out of it, I'm not doing this to hurt you, I just know that to be a good partner I need to make sure I'm meeting my own needs" or whatever it is you want to get across to them.
Happiness will never come to those who fail to appreciate what they already have.