hey, thanks a bunch for playing! i'm really happy to hear you've enjoyed your time with it so far.
to answer your first question, you can save the game in any dead end room by picking the "rest" option.
regarding the second, i may not have any good news for you. rpg maker 2000's fullscreen is notoriously wonky on newer operating systems. if the fullscreen and resolution toggles (F4 and F5) don't give you any results you like, you might have better luck downloading the EasyRPG player, which has a much better fullscreen mode. the tradeoff is that there might be a few bugs or graphical errors since EasyRPG interprets the game code a little differently than the native player does - but it should still be fully playable. if this doesn't work for you, let me know and we can try to figure out something else.