OP,
Ok, I went back and read some of your other posts...I'm removing some of my harshness.
To be fair, she said "a lot", and by no means is one kid "a lot". BUT, you said it was very difficult for you to have that baby, so I think it is fair of you to have changed your opinion and view on having "a lot".
So, some things:
1) I am not a fan of people getting pregnant at 35 or older (for the man or the woman) as many issues have a greater change of happening including Down Syndrome beginning at age 35. So, not sure when you and/or she will be turning 35, but if you want another kid to come from you both, you'd better put on the Luther Vandross music yesterday.
2) I agree with another poster that adoption is a good idea, especially since you two had trouble with your first one and you are not ideally young to be producing a baby.
3) The ultimatum is a really bad sign. My wife would NEVER put me in such a position, and I would NEVER do that to her either. That is NOT a loving gesture at all, and it is a big problem and worthy of marriage counseling if the two of you decide to stay together.
4) Based on your account of all of this, my impression is that your wife is immature. You two had a hard time with the pregnancy in some way, you are mid 30s, you waited until your kid is 3, and NOW she gives you an ultimatum about having more. Is she familiar with calendars and the passage of time?
5) I know that love is a complicated thing, but I personally would have a VERY hard time being given an ultimatum about such a big decision. If my wife ever did that (she wouldn't, because she is the best human ever), we would need some serious marriage counseling that would have to end with her deep apology. Good luck.