Okay, lets see what kind of answers I can make up here!
1. MC is absolutely an unashamed pervert, but is self aware enough to realize when and where he should let that side of him show, people usually see him as being a fairly normal (if slightly eccentric) guy, that's before they get to know him anyway.
2. I don't know if I'd call the MC blunt, he can use tact when he has to, it's just that most parts of his adventure don't call for it, so he finds being straightforward easier.
3. Maple and the MC live in the same small town (think Pallet Town but slightly bigger), it's the sort of place where everyone knows everyone, so Maple and MC's Mom would probably know each-other, but they wouldn't be exceptionally close.
4. Maple is pretty reclusive when she's focused on her work, before the events of the game, MC only really knew her as "The hot scientist who lives nearby", it doesn't help that MC usually only pays attention to T&A so wouldn't have bothered learning about her home life.
5. MC like to act like a scientist and does genuinely believe in Maple's cause, but there's no hiding the fact that he's in this for the thrills, both in the adventure and in the bedroom, Maple considers him an Asset (and lover if you boned her), not a researcher.
The update is going fine, I think I'll go through with the plan to release it in two halves.
Half of Sinnoh will actually be as much content as the game had on its initial release, plus that will cut down on the wait for you guys!