Hmm, I have no success to give advices, and can't make just single game because beat myself by feature creep.
But IMHO:
For single player game, it's no too hard to use variable timestamp or as dirty way just use smaller phys-timestamp and accumulation. It's give some notable fps spikes with low fps, but I think satisfy more peoples. (Except with really potato PC)
Price, hmm, as people from country with expensive dollar I can told so $2 or $5 makes almost no difference rather than just a free game :P
By my observation, most peoples just buy or pirate game regardless of $2-$5 price...
And as noticed by some devs on steam, yes cheaper games get more sales, but it's give no more profit without being random viral.
And about level size: I think best option to just do what You like yourself enough happy to continue development without burning. As Your current style really fun and unique enough for me and i hope for many more people with steam release. (it's still 26 review at now, but it's still 100% good! And I can remember a lot of steam release with far worst results even at couple of years from release)