” ... if Donald is the leader going into the convention and he is not the nominee, I am done with the party.”
There is a difference between a plurality and a majority.
If Trump has less than 1237 before the convention, then he needs to brush off his Art of the Deal book, and find a way to get the first-ballot votes he needs. After the first ballot, however, all bets are off.
Well apparently you haven’t been paying attention
Trump can still have a majority, if Kasich and Rubio delegates are locked out of the convention, the number needed drops.
However 1237 would guarantee the nomination, and Trump can still do that
Cruz and Kasich are mathematically eliminated, they should drop out for the good of the party