Why does my boyfriend threatens to break up after having a good conversation about a future?

This is the 4th time he has done this after a trivial argument he started and I'm getting fed up. The argument was about why I'm pouring 1/2 of a lemon into my cup of tea instead of 1 whole lemon and said I wasn't taking care of myself for that reason. So suddenly he started saying ''How would you like it if I were going to clubs, flirting with women and coming drunk, you wouldn't like that either right''. I said no and he replied ''same thing when you've just poured 1/2 of a lemon''. Then he kept going on and on and threatened to both break up and block me and I keep making too many mistakes.

Just yesterday we had a nice, conversation about a future together, getting married and having a family. Then he would expressed that I'm nearly the perfect woman. I'm confused. How does one go from wanting to marry you in the future (the highest position in a relationship) and considering me nearly perfect to wanting a break-up, which equivalent to getting fired on a job. That seems extreme.

What's going on? I'm still confused on how someone can have a romantic conversation about marriage and kids to suddenly go into a verbal tirade and threatening a break-up along with blocking me too?

Updates
3 mo
Going from wanting marriage and kids to wanting to break-up and blocking you are extremes.
Why does my boyfriend threatens to break up after having a good conversation about a future?
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