Glad you're enjoying this great game
To answer your questions....
1) When moving air units the hexes with red dots on mean if you move to that hex your plane will not have enough fuel to reach a friendly air base (note that it will not take into account the fact you may secure another airbase) Once you start seeing red dots in hexes it is best to move back to resupply. You should not need to return to refuel after each strike, when purchasing planes the fuel stat is important for each hex moved = 1 point of fuel (you will use a minimum of half your move in fuel each turn not spent next to a friendly airfield) Oh and to refuel you need to move next to an adjacent frindly airfield (or on top if you will end the move with 0 fuel) or fighters and tac bombers can refuel if they end their turn on the same hex as a friendly carrier.
In short - Just keep an eye on your planes fuel but don't feel the need to refuel every turn!
2) Not that I'm aware of...though there are some great looking mods I find the basic game far from basic and good fun
