I prefer weekly fast every month and 24 hours once a week and regular OMAD. This way I don’t have to put through the excruciating experience of 30 days fast. I would suggest you gradually increase. First try 3 days and then week, 10 days and see if you can gradually increase to 30 days. Every body is different and reacts differently. My suggestion is to progress in your comfort zone. Good luck.
Your longest fast is 68 hours. 720 hours is a huge leap from that. Most experienced fasters would find 30 days difficult. Ease into it. Try for a 7 day fast first. Even going from 3 to 7 days will likely be a challenge. Listen to your body and end a fast early if your body tells you to.
Both sounds like disaster.
Eating 250 kcal OMAD sounds like a pain to live with and will just through you out of ketosis making it harder to get back to fast after that.
Doing 30 day fast when you longest fast has been 3 days also sounds like crazy idea. What’s the rush? Do another 3 day fast if you feel okay make it 4 day fast then take a day or 2 eat on maintenance then go back do 5 day fast. See how you feel maybe extend to 6 days take a break.
Why jump into extreme fasting without preparation. Set realistic goals