Firstly, thanks for trying out my demo! I completely agree, SRPG Studio is already proving fantastic. It CAN deviate from Fire Emblem's norms if one wishes, but it's by and large geared towards making games very similar- and I'm completely okay with that.
To answer your questions:
1) Yes! I haven't yet figured out how to bring up an indicator that you have advantage or disadvantage on-screen (I've seen it done in other projects, though), but it follows the same triangle as the Jugdral duology. S>A>L, W>T>F, L<->D. Within the engine, you can define what weapon types have what advantages over what other weapon types under the "Config" > "Weapon Types" settings.
2) In my game, Daggers are the weakest but most accurate of the physical weapon types (continuing the progressional tradeoff between the others) and stronger variants are planned to have higher critical rates to compensate the lower might. They're mainly for Thieves, though, which aren't meant to be combative units anyways.
3) Stronger Bows are planned to have increased ranges- you can actually see this already in the demo on Hard Mode, in Chapter 2 another Archer appears with a Medi Bow, which has 1-3 range. Essentially, my philosophy is meant to be a "pick-two-of-three" triangular relationship between power, accuracy, and range. It'll show itself more as I progress in working on it, and I plan on releasing more demos down the line to get feedback.
Thanks again for playing!