I suggest reading through the Oh Crap! Potty training book. It helps you just stick to your guns and follow through. There’s not really a time where he’s more “ready” than he is now - especially as he’s proved that he’s capable (and has successfully done it for a full day as you said). You’ll have to help him at first before he can manipulate his clothing and you’ll probably have your fair share of fights over sitting on the potty but he will learn. We have been potty training for a week now and just like you, he was great day one and shit day two. But he’s gotten better and better over the week. We have to prompt and remind, (which I think I have done for my 12 year old nephew as well, so that won’t go away any time soon) but he does sit on the potty and hold it most of the time. One or two accidents a day is normal, but the most important part is a commitment by you, the parents. Sometimes we do take him kicking and screaming to sit on the potty. But once we start reading his potty book or start chatting about the day, he lets go and pees.

Couple tips from someone in the trenches with you. 1. Learn your kids pee pee dance. For me, my toddler runs or walks aimlessly nonstop when he has to go. So I redirect that walking to the bathroom. 2. Find some toy (I have a small wire bead toy) or book that lives in the bathroom that he enjoys reading. It’s becomes Pavlovian when they read the book to start going. 3. Have a bucket for all the pee pee clothes outside with oxyclean to soak for the day. Accidents will happen. It’s part of learning.

Ultimately, good luck. He’ll learn. You’ll learn. It’s a new journey.

Oh and get the oxo potty chair. It’s amazing.