Those that did the Ferber method

Ok so she used to go to sleep fine at night, wake up after 4-5 hours dream feed then back to sleep. I could lay her down no issues even if she opened her eyes she’d go right back to sleep. Since the top teeth started coming in sleeping got worse. Now I can lay her down but she’s usually up within an hour, after that there is no getting her back into her bed I’m not sleeping with her next to all night! And naps, I used to be able to lay her down and she’d sleep now she wants to be held and nurse for all her naps. So I tried for her morning nap the timer. Laid her down awake but she was tired. She fussed when I walked out 3 min timer came back in she was fine but not sleeping. Left the room soon as I did she started crying, 5 min wait (did the dishes), came in she was crying but not fully upset. Calmed down a little left the room started getting more upset. 7 min timer swept the entire house. Came in tried to calm her down she wasn’t having it. Left again another 7 mins. But during this time she was so upset she was struggling to catch a breath. The crying kills me but my question really is how long to you keep going in and out before you stop and try again the next time? How long did it take? I feel like if I keep going in and out or with how upset she gets she’s not going to be able to breathe. Like a few months ago she was having a rough night and dad thought he would try to comfort her and get her back to sleep she was crying so bad she couldn’t get a breath in or make a sound when I woke up she was almost blue. Soon as I had her she calmed down but was doing that sniffle thing people do after crying really bad and did that for 6 hours while sleeping. Sorry it’s so long but I just can’t keep holding her for her to sleep. I’ve lived in pjs for 8 months now because there is no time for me you know?