Hard for anyone to say what is right for you. I have a croix de fer (similar geo to cda). I am 5ft 10 and 33 inside leg. The 54 was OK but felt a little cramped and I was getting toe overlap. Off road it would have been fine. I wanted comfort and slightly higher bar position (less saddle to bar drop) so went for the 56 but dropped the stem from 130 to 90 and it’s spot on.
I could have easily got the 54 to work to. Guess you really need to sit on one and see how it feels!
I have a mate who is taller than me on a 52 cda and perfect for him.
It’s all really too personal to give remote advice…. But I would say medium (54) would be fine 🙂
Usually advice is to size down for cx but that’s a load of rubbish. Get a bike that fits.