Try to westernize as soon as possible. The amounts of Monarch Points drained every month depend on your income. 15/month is probably the first and only threshold that matters in the case of 3M. As most of your income will be from trade (Hangzhou and Ceylon), you may recall your ships (or send them as privateers against your rivals) and merchants back to stay below 15. In my game, I came down to 14.5 Income/month...unfortunately during the westernization, my income increased over 15...so i sent all my marchants and my fleet back to get about 26 Gold again => 27 Points drained per month and it was still no big issue.@ Tortugator:
I've gonna give it a go your way after yet another failed attempt. Ended up with really bad timing with high OE after a war, ruler die and low legitimacy heir take the crown. Rebels became uncontrollable.
Your method sounds a lot more versatile and shouldn't require anywhere near as many restarts.
One question I have is how much conquering do you think should be done before westernization? I finished a game as GH for the Great Khan achievement and thought I'd go ahead and do the westernization achievement after. It took several decades to complete because of my huge tax base. I am wary of expanding too fast before westernization but certainly don't want to wait so long that the other regions power consolidate and inhibit further expansion, Timurids I'm looking at you.
Use your Military Points for Harsh treatment on your colonized islands (you don't wanna fight Rebels there) and try to have at least one large Vassal who kills the Rebels for you. I'm not 100% sure, but from what I observed, Vassals tend to kill your Rebels only if they have a larger army. They will NOT coordinate, however, and only follow you into the battle if their army is smaller. So if you have 2 Vassals with 5k Troops each and you have an 8k Rebel stack, they will NOT kill it. If you have 1 Vassal, however, with 10k Troops, he will kill it (if he's near).
In my game I had a fully sized Bahmanis killing most of my Rebels on the Indian subcontinent.