HB that sounds really frustrating. My DD is a sleep fighter as well. She will be so tired she can bearly keep her eyes open but she will tell me shes not tired and try and stay awake. Asks for stories, tickles, any tactic to keep me talking or engaging with her.

IMO gentle parenting doesn't necessecarily mean no crying ever. As they get older they are going to cry when they don't get their own way. Can't always give in to what they want. You know he is tired and know he needs to go to sleep. With my DD sometimes I have to leave her alone as my presence is stimulating for her. She is a bit older though and understands the "I will be back in 3 minutes to check on you". Generally when I go back to her she is asleep.

I hope you find something that helps.