Well reasoned, but there are 885 delegates remaining and that throws the math off. Trump has to win over 54% of those remaining delegates. Cruz has to win over 87% of them to win. However, if anyone other than Trump, including uncommitted, get 483 of the remaining delegates, there is no first ballot winner. Cruz still has to win two more majorities (he has ID,KS,ME,TX, UT, WY), or he cannot receive votes in any round.
It’s majority of the delegates (50% + 1 of delegates) not 50% of overall % of vote, I believe. There is a significant difference. I may be wrong but I think that is what it is.