Besides being a classic "marry me!" joke, it's a reference to a vision Being X showed Tanya in older chapters, where Visha was portrayed as his ideal wife in his old life. I don't know how long you've been reading this manga, but the idea that Visha is such a perfect adjutant that she's basically like a "ideal wife" for Tanya has been around since the very first arcs.
Yep! Once we’re caught up with all the main chapters, we’ll work on all the spin-offs/side stories. We already have some of them translated, ready for when we start working on them.