Giving parents effective tools to make their needs and expectations known, in a way that is not only considerate of the child's needs but also makes them part of the problem-solving team, is the heart of the lovely little book, ow to Talk So Kids Will Listen, and Listen So Kids Will Talk.
You will be delighted with the peaceful and mutually supportive techniques the authors teach. It's my favorite with my 4.5yo grandson. We just had a 3-day sleepover, and I used what I have learned from How to Talk/Listen from beginning to end. What a team we were!
Try sitting down with your son during some moment he's a bit distracted by a game of his own. Tell him what you wish for in positive terms. For example, "You know how sometimes you want to have a little bit of quiet time to do your own thing? Sometimes Mommy needs that, too. Do you have any ideas how you can give Mommy some more time to do my work? Let's make a list together, and I'll write down ALL of our ideas!"
Kids are flattered to have their ideas taken seriously and written down. Don't cull any ideas during this brainstorming session, even if they obviously won't work. Coax as many ideas from your son as you can, and put down several alternative ideas of your own. Then go through the list together and choose two or three that could work. "You could take a nap when you get home." "I could read a book in my room until the timer dings." "You could work on a project, and I could get the supplies and set them up for you."
Because he will be part of the problem-solving team, he'll be invested in making his solutions work. And he will have taken your needs seriously during the problem-solving list, possibly in a way that has not touched him before.
On the bed wetting, peeing during sleep is really beyond the child's ability to stop, and some children will experience flurries of this when entering new developmental stages, too. And this regression is extremely common when big changes happen in the child's life. It's temporary. I'd give things time to settle and your little guy a chance to adjust before you additionally require him to give you more space. That could simply exacerbate the bed wetting.