Oh, to be Clear: I'm not saying you shouldn't do social media marketing -- it's obviously Necessary in your particular niche and as you wrote, it can't hurt you at this point. What I'm more so suggesting is to be cognizant of how you approach it. Step up your game(punny)if you believe it's necessary; but I'd also make sure to research given your general audience and those you'd like to target in the future. For example, I run an artist studio and out of ALL the sm options out there, FB is most effective for getting sales and beats other sm sites by Miles. As a small team, wield your energy wisely. Go for the sm sites that will give you the most proverbial 'Bang for you buck'; ask/see what other devs are using that's effective. But also figure out your 'Lines'.
As for Heaven's Grave being GxB only - I mean you're Always going to Limit when you restrict romance options -- but there's a HUGE GxB otome base out there so I don't think that was a major setback. I also believe you mentioned something about an all GxG(which I would support the HECK out of)you had in mind; as long as you provide a fair amount of all options in your games, I don't see an issue.
It's Absolutely Fair that you want to get BFF out for those who've waited; yet I'm worried(as I'm sure you are) you may end up having another HG situation on your hands. A Kickstarter may help - but there seems to be a lot of distrust there. Since ToW is a sequel - at the Very Least you're not starting completely Fresh: You have a Dedicated fanbase (who all have their respective baes) that have already enjoyed RoS and are Very willing to see the Continuation of their adventures. From a Risk standpoint, it's a Lot lower than BFF--given your financial situation. Again - I think a poll/survey is the way to go (to Start) and I hope it gives some valuable insight. Then you can see where the winds are blowing. (If BFF fans are willing to wait if it means getting ToW sooner, etc.)