I don't have an answer for you, but I 100% support your journey. I've made the move from full time gigs to 20~ hours a week upper bound of consulting / freelancing and I couldn't ever see myself going back. Good luck!
Is that 20 hours the amount of time you're billing weekly, or your total work time? I aspire to freelance one day, perhaps soon, and I've heard that non-billable work can easily add up to a full time job. Things like marketing yourself, connecting with clients, possibly administrative things to do with your business.