Males are usually pretty fine on their own. They are kind of like territorial dogs, hehe, and considering all the research you've done and thinking you've done on this subject, I know you care about your mice very much!
So as long as you give him lots of one on one, you can become like a big daddy mouse for him. HEHE. As for Decible, perhaps a cagemate would be helpful, especially considering that there is a possibility she may be pregnant...she may get moody and lonely.
I am glad you are doing the right thing for them. And with mice, the more the merrier, so if you do get her a cage mate, happy selecting!!!