Hiya.
I've not posted for a while but I've just had to go down the route of CC. Like you I had tried everything and nothing was working, he was waking every 45 mins and staying awake for an hour each time .....don't know how we were all surviving!
Anyway first time we tried controlled crying he was 7.5months and I still fed him twice in the night, it kind of worked within a week and was waking a few times a night just to be fed then would go back down for a few hours, I was happy with that but then in the second week he started being more and more persistent particularly at times when I knew he wasn't hungry as he had just been fed. And then he got worse with waking 10-12 times a night,
Health visitor advised me to cut out the two nights feeds. I was hesitant as I was worried I would be hungry. Anyway on doing the CC properly second time (8.5 months) with no night feeds on night 3 he slept through and he has been pretty good since. He is now actually feeding better in the daytime too
and goes down with minimal fuss and always within 5 mins.
Are you still night feeding? Health visitor says it can send confusing messages about what night time is about and then they can wake at the end of sleep cycles (45 mins) wondering if it's time to be fed!
Also helpful was making day and nighttime very different and decide on what time morning is and go into her room with smily face, lights on and bright voice (opposite to any night wakings).
Good luck with it. It can be stressful but it is worth it!