I have published two other books which have sold reasonably well for self-publishing. I think its very true that the more books you have the more you can sell - cross sales etc. I have started to do a price drop each month which increases sale numbers and I pay for an advert to generate interest.
I am not too constricted by genre which is probably not the 'done' thing. I write what comes to me. My current WIP is a bit more ChickLit for a total change and I have a historical novel in my head which may well be another time-split.
I'm on the point of publishing and thinking along the prequel lines or serialisation. My book is also a bit cross-genre which is probably a problem for traditional publishers but less so for indie as you are proving: as we don't have to worry about the profit line but can be more original for the story's sake as you say.
Yours are a bit chicklit its true or I would have offered more feedback (I looked at the train carriage one). But I might delve deeper to see how you do the time split.