The rules are written quite clearly for V-3.
Allied Support: The Allies may send Lend Lease Supplies (upgrade 1 militia to 1 infantry. Price 2 IPP) to both factions. Only one Allied Power may send supplies per turn.
That is all the Allies can do!
The Spanish Civil War is a Historical Event within the game and you must follow the rules for that event regardless of what the reference sheets say. After the Civil War has been decided then that ruleset has been completed, which means you can treat the winner as a minor power.
You don’t count any of the points until after the game. If the Nationalists win the civil war then the Axis can potentially collect the point for Germany and the point for Italy when the game concludes. Remember that you have to be in possession of your capital at the end of the game in order to count any points so those points aren’t actually guaranteed. The points for the Comintern and Allies are awarded as per the Victory Points rules and don’t hinge on who wins the war, although the Comintern obviously has a better chance to collect them if the Republicans win the Civil War.
The Russians can’t possibly win the Spanish Civil War because they aren’t Spanish and wouldn’t fit within the definition of a civil war in such a case. That of course would be assuming you could ignore the rules of the Spanish Civil War and in particular those regarding Russian support that are listed along with the Axis support and the Allied support that I quoted earlier.
The V-3 rules of the Spanish Civil War are an upgrade from the V-2 rules. You don’t need any special pieces to play it so do yourself a favour and substitute those rules into your V-2 game. The entire V-3 game is a much better game than V-2 and was created to fix the issues that arose over the years. It’s a lot more fun to play too. You can use coloured chips to differentiate between cruisers and other units that you don’t already have.
Also know that if anyone tries to break the game by taking advantage of the way the rules are written to gain an unfair advantage then we will change the way they are written or change the rules to close the loophole that they may have discovered. Our goal is to make it the best game it can be. Please play the game with integrity and let us know if you find a problem with it. In many cases it is a simple misinterpretation of the written rules like in this case.