Nice Guide! I was literally making one up myself since no one had posted one. As someone else who has the Mad Skills Yo Achievement I would agree with everything you put in here. I used Molotov as well!
I would throw a couple things out there though on Romeo and Kiriko I was able to do Facebreakers even on Impossible. I'll just add in my two cents just for reference.
Romeo: The trick I used to get this guy is to get him to drop his parry. You can do that by swinging a haymaker at him (kind of sketchy and hard to hit him) or just swinging high, letting him swing at you and dodging one of his punches. Then the trickier part - what you have to do is constantly throw LOW hooks, but your timing needs to be throwing it as soon as he gets his block up. What happens is he will parry your hook, but he doesn't do it perfectly, meaning you can dodge it - you need perfect timing - and throw another hook. Then you wait for roughly a second and throw another hook as he is recovering and getting his block ready again. 30 seconds to Facebreak this fool on impossible
Kiriko: She is REALLY easy if you are good at timing your dodges. Simply throw a hook at her, she will dodge, counter dodge and hit her with a hook. Throw another hook...rinse and repeat until you have a facebreaker powered up and throw it after dodging her and throwing your hook. If you have trouble with perfect timing on the dodge this will not work and is actually a terrible strategy as if she throws a hook, you dodge it and she dodges yours and lands a punch you will be stunned. So perfect timing is a must. 23 seconds to Facebreak her on impossible.
Really though this is just how it worked for me and it made it go even quicker... Excellent guide!!!