When I said to leave the two email options alone (for now) I was talking about the two check boxes at the top of the same page where you selected what calendars to sync. I only said it because, one, I'm not completely sure what they do, and two, I didn't want to add further complications.
If you are talking about keeping both the old IMAP and Exchange account, I only meant for you to keep them both if you want to continue syncing Notes to your Gmail folder. When you look at the sync settings on both accounts you will see that the IMAP one offers Mail, Calendar, and Notes syncing. The Exchange version offers Mail, Contacts, and Calendars. To keep Notes syncing you turn OFF everything except the Notes sync option. I never meant for you to have Calendars on in both settings. Same goes for Mail. Only leave it on in one of the accounts.
Or if you don't care about having Notes synced to GMail, delete the IMAP account and save yourself the confusion.
IMAP and Exchange are just two different ways of syncing your email. Each has it's own advantages. Google supports all three main email protocols (Exchange, IMAP, POP3). I had you switch because the Google Exchange (using ActiveSync) supports multiple calendars. As a bonus it also syncs your contacts (though it does not support groups/labels) The IMAP method only syncs your first calendar.
Each protocol has its advantages/disadvantages. For you (and most of us) the Exchange account has the the best mix of features.