Well done, Brendan! You’ve set some lofty goals, and it sounds like you’re taking all the right “steps” to reach them!
Your trip up Whitney sounds great. Taking a week to do it will give you additional time to acclimatize and really enjoy the experience.
And I cannot recommend the JMT highly enough. Many of the PCT thru-hikers we met on the trail agreed that the JMT is one of the most if not THE most beautiful section of the PCT.
Have you seen ‘Mile…Mile and a Half”? That’s a great way to whet your appetite for the JMT.