Buy to close Jan $350 calls for $29.79, breakeven $379.79
Sell to open Mar $365 calls for $23.91, breakeven $388.91
...
I don't understand in what sense $379.79 is a breakeven?


The first line is describing the situation of the position I had before the trades, assuming I did nothing more till it expires.

The old position ($350 call written for a premium of $29.79) had a breakeven of $379.79 in the sense that, had the stock price been high on expiration date, that's how much money I would have received for my shares that got called away.
$29.79 that I received on the day I wrote the call, and another $350 on the day that the option expired and the shares were called away.

If the stock price were to end up in the range $350-379.79, the stock would have been called away, and I'd have done better having written the call than having sold the shares on expiration day. Call good, selling stock bad.
If the stock price were to end up higher than $379.79, the stock would have been called away, and I'd have done better not having written the call, then simply selling the shares on expiration day. Call bad, selling stock good.
If the stock price were exactly $379.79 on expiration date, the stock would have been called away but it would be a wash: the breakeven point between the two cases above.

If the stock were below $350 on expiration day I'd have just pocketed the $29.79 premium.

Jim