I don't get Barry's logic here. He knows for a fact that the past can be changed, so why would he ever think the future can't be? His plan is to change a bunch of other future events that have nothing to do with Savitar and hope that that makes Savitar just... lose interest or something? Seems to me what they really need to do is figure out how Savitar comes back and why he kills Iris.
I was wondering why they were asking HR to explain how altering the timeline worked. Didn't they decide HR is a science fake who doesn't know what he's talking about? And Barry has actually changed time on several occasions? So why is Barry asking HR how it works?