PLEASE HELP ME!!!

I have been stuck on the mission "Into China" on moderate for a week now. up to here (JoA, Barbarossa) the game has been the perfect balance of challenge, fun, and ease, but the game won't let me do anything all of a sudden. I can take the engineers out no problem, but no matter where I build my base, I can't get at the gold or stone without being slaughtered. If I wall up in the hills, with the gold/stone in my base, the reds, blues, and greens all swarm me with arbalests, rams, scorpions and light cavalry. No matter how quickly I get set up (imperial age in 15 minutes) I cannot hold off all three of them at once, especially with my limited resources and their head start. They take out a castle in 3 minutes flat with only archers, which is bullshit bordering on cheating, considering they are using weapons that didn't exist at the time (a crossbow that shoots 20 shot bursts every 1.3 seconds? WTF!? That's not physically possible!)

If I build my base on the engineer island, that goes really well as far as defense, especially if I get the bobard cannons. (between two onagers and 4 bbc's nobody reaches the gate) But then I quickly run out of resources, as they hit any mining camp I make with 5 rams, 5 scorpions, 5 light cav, and 10 arbalests/cho-ku-no before I can even get any profit. I feel like I'm on the hardest dificulty, when I'm on moderate; I have only occasional pauses when I am not under attack, for about 30 seconds, and I can't get any gold. If I go to the yellow island at any point I have the same problem, only exacerbated. The one time I managed to trade my way to enough resources, they killed a pair of castles with archers. Literally nothing but archers at such a rate that I couldn't mine enough resources fast enough to trade them for stone and repair the castles, let alone taking ground. The yellows don't need siege equipment! They're taking my castles out with more success with archers than I have ever seen even with trebuchets. If I attempt to use the same units as them, and upgrade them all the way, they still get massacred.

I feel like the dudes at the end of The Last Samurai. I am really beginning to feel like there is no possible way to win without cheats. I have used every piece of advice I have gotten, and in a normal level/multiplayer they would have worked, but everything that works for everyone else is being raped by these people. Even the yellows alone will spam me with units faster than a pair of side-by-side castles can kill them. What the fuck am I missing!? Please help me!

P.S. If you say Mangudai, I will look for a way to delete your bullshit comment. I upgraded them with every upgrade they get bonuses from (I had to cheat for resources to do it, mind you) and then watched 20 of them, which I felt to be a good force, get pwned by 5 arbalests. Without landing a hit. Smiliar results with the cavaliers (they managed to kill 1 out of 5 before dying, even whilst all attacking the same dude at once.) Mangudai are uselessly grabbasstic pieces of amphibian shit. Please actually help me. I can't beat this level with cheats, or I'm simply going to stop playing.

Edit: I even tried baiting the yellow cavaliers to my castle, so I could get some villagers in there the way the speedrunner dude did it in 16 minutes. Every dude I lure away is replaced by another one immediately. Oh, and did I mention my version of Jin (the yellow team) have cavaliers guarding the place everywhere, which that speedrun dude didn't? I can't even get to the base without being swarmed. Which kinda illustrates my point of this being unbeatable/the hardest it can possibly be, considering that dude plays on hard, and his version of the base was practically unguarded.