Bit the bullet and took the exam 6 weeks earlier than originally scheduled. Came away with an 829.
I'm pretty pleased. The exam was not as challenging as I'd prepared for.
I want to say a big thank you to everyone here who provided advice and encouragement. So: thanks a lot!

I used the Meyers book, both Mike Harwood books and the N+ Passport, as well as Prof Messer's vids.
Time to up the ante now: the 70-680 exam