Just to explain to us outside observers - where it the impasse exactly? Is it truly impossible to begin the bedtime routine earlier starting tomorrow or next week with some planning and schedule changes? This is one case where I agree on both of your issues and think they are very important. What I don't understand, besides the possible logistical issue of ACTUALLY starting the routine earlier depending on dinner, etc., is WHY both of these issues cannot be addressed. To me it would be an impasse if H said I want him to have a 10:15 bedtime but he really doesn't SEEM to care about the bedtime per se but about his issue or if you believed that your son should learn to NOT complete tasks. I do not not think either of you believe those things. That is why I (and I assume others) keep asking more questions about the real issue at hand.
Whether your H has said this is finished or not is not really relevant. He may feel frustrated and be afraid of further failure on this issue. So it may be easier on his ego to just "not give anymore". But like I asked before, is it possible to deal with this issue without him giving at this moment? I would convey to him somehow that you do not want him to GIVE. What you want is to give him the room to complete tasks with S6 without staying up too late.
It occurs to me that both of you may be feeling this small issue is a larger magnification of the larger issue (and in some ways it is) but by seeing it that way it can also make it a much tougher task to address than if it was simply a combination two good lessons for S6 being accomplished at the same time.
OK NOW I have to get ready for my meeting!!
But what is happiness except the simple harmony between a man and the life he leads? ~Albert Camus
