Saddened to hear that your campaign turned out to be a failure. By the looks of your save file in 1660, here are your major mistakes for the last 20 turns (I am mentioning this so you won't fall for it in the future):
a) Letting Elizabeth be first in liberalism. This is seriously a game breaking mistake! You are roughly in the tech lead by 1480 AD but your vassal out-teched you in liberalism as she gained momentum. She is now your vassal and she is a good techer. It is your duty as the master to dictate what technology she should research and then trade for it.
b) I noticed that when the AI demands something, you always give it to them (even with Gandhi). This is a big no-no as they will get too advanced and you will have a hard time fighting their advanced army.
c) No HE still. Unless you want a challenge
d) You are relying for slavery too much for army production. Slavery is starting to get inefficient in unit production during renaissance. You should work on high hammer tiles or go for drafting (using Nationhood)
e) You declared war too early. Like I said in post #109
Your economy is not good. You can't afford to go to war and is not profitable yet.
f) You conquered Delhi but you forgot something I mentioned in post #109
Gandhi has a double-religion holy city (Delhi) but no shrines . Having built the AP, let him pop up a Great Prophet to build one his shrines before you conquer it
No shrines == no gold per turn. You conquered a useless holy city. UoS and AP is not helpful.
g) You fought a war without assurance that you can win. You win the war
only if the AI offers something in the table. Let me show you something:
This is your info screen at 1480 AD:
This is your info screen at 1660 AD:
As we can see in 1480, you are 2nd in mfg. goods (prod). Gandhi is the first here by checking the graph. That means he can outproduce you in army. In terms of population, you are 2nd but the difference between the 1st (Joao) and 2nd (Qin) is big (20-30% more). Therefore if war starts, Joao can whip more army than you.
By 1660, it gets worse. Mfg. goods (prod) made by Joao (1st) is outproducing you by almost 300-400%. The only way to beat him is to have more advanced army. Population wise, he is 30-40% bigger than you. In simple terms, you are fighting a bigger army here.
I hope this makes it clear why I mentioned "Joao's army will swallow you alive"
h) You did not utilize the strengths of your traits. Most of the time, forges (industrious) are important buildings next to granaries. You did not focus on choko-nus (free drill 1 and CG1) instead go for maceman (no promotions). May I know the logic for this?
j) Your research plan needs improvement. Your plan to research military science is already too late. Joao has cavalry. Instead your tech plan should be to rifling.
k) Your city tiles needs rework. I and Amao mentioned that you should go for workshop. But you must not neglect the food. I haven't checked the latest save but in 1660, your "mined banana" is still not turned into a plantation. Making your capital unable to work on the workshop you just generated.
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I am sorry to say, your situation now will force you to tech until rifling or industrialism to secure a win against Joao (assuming you avoid additional mistakes in the future). Thus, delaying your victory.
If you want, go back to 1480 and redo your strategy.