I've been trying to broaden my product line to appeal to D&D players as well, and that allowed me to sell a lot of copies at Gen Con that wouldn't have moved otherwise. Half of my poster maps are now genre-neutral, meaning they can be used equally well in Star Wars, D&D, or even modern or horror RPGs.
That said, I think there's still a lot of strength left in this community, and the success of both of my Kickstarter pre-orders stands as proof of that to me. They have made it possible for me to stay invested in the SWM game and this community. I know there are those who've told you that SWM is fading away and you'll no longer be able to make a profit catering to it, but I disagree. It may eventually become true, and doing 100% distribution-based sales will eat into your profit enough to make it feel that way, but I think you can still do sci-fi minis maps and make a profit in the process.
I would definitely recommend Kickstarter. Let me know if you need an invite! Set a funding goal that covers the cost of the print run, and if it's successful you know that the job has at least broken even. The sales of additional copies then becomes your profit, and lets you afford to do a 50/50 split with copies sold through places like MM (or even a 60/40 with a mainstream distributor).
I know Steve was giving you a hard time about your packaging...that's one area where you might want to consider his opinion; he knows what sells for him, and face-to-face sales like at Gen Con will benefit from people being able to see on (or through) the packaging to know exactly what they're buying. Your existing packaging is fine for mail-order and Internet sales where you can post jpegs in the product description, but if you ever want to do retail or more robust convention sales, look into ways to make your product eye-catching on a shelf.
As for single-map sales: it works for me. You've gotten good mileage out of combo packs in the past, though, so I'm not sure if you'd want to abandon that. I think you could sell your maps efficiently either way. Just make sure you don't devalue them in the process. You need to charge enough for your product to make it worth your while, and if you charge too little you're basically paying for materials while giving away most of your time and effort. Conversely, charge too much and you won't sell enough to cover the same costs. (I think the price of a booster is pretty fair for a double-sided poster, but that's just me.)
Anyway, I hope you decide to keep producing maps and wish you luck with everything.