Playing 3 nations in semi-secret is always a recipe for potential disaster - sour feelings and personal conflicts. I've seen this many times already. I myself has been subbing for nations for long periods - like 10-20 turns, but it was always clear it is only a temp thing and if it was looking like the original player will not return, it is your duty to report to everyone and ask what is to be done or either find a sub for THIS NATION or to put the nation to AI. But playing a nation to benefit from it and not helping improving the playability of this nation so the original player to want to return or a possible sub to be found (like in your case giving them unit so you dont pay maintenance, taking away their money for no clear reason to fuel your own nation, not teching for this nation, etc), this is terrible unfair thing to do. I subbed for OzzyKP - admin at Apolyton in "Destiny of Empires" pitboss and had won him a World War which he was losing badly (he was the score leader and got dogpiled by 3 other nations) and got back under his control almost all of his cities which he was lost during that said war (he had lost like more than half his cities initially and despaired) and got his enemies to pay him money reparations, where I asked nothing for myself, despite my original nation and Sommers fought damn hard to help Ozzy's nation revival happen. Once Ozzy saw his nation is winning the war and he is getting in actually better condition than he was when he left, he returned and played his nation until the very end of the game. This is how you sub for a nation. Not to keep them in the dark ages and fund yourself. Another case is Gods and Heroes pitboss where I subbed for MZprox his nation where he was dogpiled by 3 nations. He asked me to sub for him while he was on vacation, but incidentally or not, it happened at the same time he understood he wont win the game because of this dogpile. He fend off one of the nations and asked me to sub for him initially until he return from vacation, giving me instructions how to play and what goals to achieve. And even my primary nation was in war with him at this time, but I was not 1 of those dogpillers, I was on my own. I of course did not sent anything at his way from my own nation as I felt that would be absolutely not appropriate. So I played for him. Managed to force his enemies to drop one by one, beating their armies, taking back his cities until he was in the position he was before the war begins. Then I asked him again to come and play his nation, but he said he have RL chores, etc, etc, but it sounded to me he is not happy with being not anymore top dog. I went ahead and actually attacked one of his enemies and managed to get quite a chunk of nice cities and land from him and making him swear allegiance to MZ's nation for peace. From this position I asked again MZ to return, as he was in even better shape than he left - he was having a game-long war with 1 neighbor, which I made an ally to him, then he had another ally on his other front and a soft victim to conquer on third front. MZ said he wont come back to the game and then I went and actively searched for sub for him. Dratboy took a look at MZ's civ, liked what I had done and took it and played it. He is around and can say if what I did for this nation was any good or not and if this nation looked as exploited and robbed. BTW in the very same G&H game, OzzyKP was semi-officially-permanent-subbing for one nation, and when the problem arise, he claimed that he did all in his power in a good faith to help that nation, but he was accused by MZ he is using his second civ to attack his main rival and slow him, while giving advantage to his own civ by transferring money - claimed for upgrades or something. Words were exchanged and beside all the swearing that it was all in good faith, it seems it was not enough and it lead to dropping out of the game for both involved - MZ and Ozzy. Later we found a sub for this civ and all was good.
So, this is how you sub. You make in good faith everything possible to help that civ, even if it is against your civ interests. Dick have no access here, but he told me he felt like robbed when he looked at his civ after he took it back. Cal showed me how you were sucking dry both civs under your control to fund yourself with money. But this was not enough. You were even having a gpt deal with one of them which was causing that said civ to go at strike and you to receive more money than this civ is actually capable of making. This itself is known exploit and cheat.
Anyway, you can always say: "But I did everything in good faith". Well, you live and learn what is perceived as good faith and appropriate and what as the opposite. If you were knew Dick left the game, why you did not tried to find him a sub? Even once? Since when was the last time you heard from him? And if you were knowing he will return, is this the situation that you were thinking he will be happy to see his civ at after you took care of it? Running around with horse archers while he funds your Space Program research? Dont answer me, answer yourself.
Whoever said that keeping Celtia under your control was maybe game-changing as other nation could have conquered it long ago and changed the balance of power is right. By defending Celtia you were defending your own interests, dont they to put it like: "Oh, look what good I did to Celtia keeping them alive", as if there was someone's interests serving best, that I think it was yours.
Actually, you are right that vassal states must be always turned off. However, this did not stopped you from fully abusing this broken for MP with humans mechanism.
So much for controlling more than 1 civ.
As for saying: "I was going to win despite you guys break your NAP, but I just dont want to bother anymore", it sounds pathetic. I dont know the in-game situation well to judge, but if you really think you can win, I think you have more than enough competitiveness and lust for the win to try do it and then boast and mock your poor adversaries.
the exact same deal with you, right down to the "till we're the last 2 civs in the game" clause
LOL, you did that Maga? Well done, girl, that is a masterful move. Guys, you should be ashamed to have fallen for this. I already said somewhere in the team thread, but accepting deals with no clear end date of a clear way to end this is not a good practice.
For breaking NAPs to avoid someone winning the game, I had such dilemma and my own decision back then was to keep my word even if this will mean I will lose the game. My personal conclusion and lesson learnt back then then was: "Think well before signing agreements"
In conclusion, I must say that so much drama and melodramatic end in supposedly more-friendly pitboss (we are all a team after all, right?) surprises me and is not normal. Something was or went really wrong.
. Forget I suggested it. Give yourself a break and shut this one down, Caledorn. 
Maga that much. 
