Heyo! Glad you like the game! :D
Old saves work sometimes. I always tell people to start a new save when a new chapter is released though, because I don't playtest the game with backwards compatability in mind. If you enable all the skipping options and skip through stuff you can get back in like 5 minutes. ( Just remember to untoggle all the skipping stuff once you catch back up to where you were though. )
I've got no clue about how many chapters in total. I have a vague story outline in my head and it's going to take like 2 years more I imagine. It's possible to add so many things to a game like this too. People keep asking for p0rn scenes of random side-characters too so we'll see.
I've got no idea what type of project I might make after this! Maybe I'll make a SFW comic or try to get into some 3D pr0n or something else I'm not sure. Making another ambitious nsfw VN right after this one seems highly unlikely right now. I think I'll want to do something different for a while. But like I said that's probably 2+ years in the future and who knows what the world looks like then.