I don't wish to waste my time replying to most things that I could in this thread, but there is one thing that jumped out at me...
What is the chance of a smaller alliance getting any forts away from you in a 1:1 fight?
I'm sorry to burst your bubble here, but the chances are actually much higher than they are in multi battles. If you think otherwise then it's no wonder you find yourselves in the situation you're in.
No matter what, you can only fit 140 people into one side of a fort at one time, correct? The smaller alliance, providing it has over 140 active members (which yours does), has an equal chance of winning a fort in a one on one attack due to the fact that the larger alliance, no matter how many people it has, will only be able to fit 120 people in the fort to defend.
Now, look at it the other day. Say the smaller alliance has 150 active members and the enemy alliance has 300 (these numbers are not meant to be accurate, just an example). Both these numbers are enough to max any size of fort on its own. However, when the smaller alliance chooses to use multi battles, they're giving the larger alliance the chance to utilise their number advantage. Say you attack two mediums and two smalls. Out of the four battles, the alliance with 300 active fort battlers would have the numbers to max all four of these battles, while your alliance of 150 members could only max two of them at best (a medium and a small, or two smalls with members left over for the remaining two battles). A more realistic scenario is that the smaller alliance would have a low attendance at all battles, or concentrate on one battle, either way would not have an effect due to the big alliance's numbers covering each fort adequately, not to mention moving numbers to one fort when they see the majority of the enemy congregating there. I know it's not realistic to expect 300 active fort fighters, but this is just an example and its principle still comes in to play; the bigger alliance may not be able to max all forts but it will be able to get more fighters at each one.
What do you think gives you a better chance of a victory? 100 vs 84 in a medium, or 50 vs 84 and 20 vs 42 in a medium/small multi?
Then you can take into consideration that the larger alliance is, in theory, more capable of launching multi battles of greater magnitude. So if they choose to retaliate the numbers would end up along the lines of 15 vs 42 at each of the big alliance's defences and then 50 vs 30 at the big alliance's attack. Wow, now the small alliances has lost two attacks and a defence just because they had in their heads that it would be easier to attack two forts rather than one when they don't have the numbers to fill them both, than have an even chance of taking a fort in a one on one battle.