Here’s the thing: Updates to the wait step won't apply to the people already entered in the wait step. When people enter a wait step, Marketo stamps the wait duration based on the wait step configuration at the time of their entry, any subsequent changes to the wait step won't transpire and change their exit time, and hence updates to wait step for the people already in it doesn't apply.
Now with that background, you can remove people from the campaign flow using Remove from Flow flow step, edit the flow to have a wait step with the correct wait period so it ends on Monday 9 a.m. and a flow step to send email #2 (no need to have Send Email flow step for email #1 as that’s already been sent). You can create a new campaign or just update this campaign and re-add people to it.