I want to be available to validate his feelings and to act in a kind and supportive way if I can
That right there is your problem..
You are not dropping that rope at all... you may think you are based on your previous way of dealing things but in this sort of environment acting in a supportive way is helping nothing.
This is about you not him... your keeping one toe in the pool testing the water all the time.
Things will not change the way you are currently dealing with things.
No wonder you sound confused, all these different ways of acting in different scenarios is just inauthentic because in the long run you will never be able to keep it up.
Without a shadow of a doubt... the best way to get any relationship in this situation back is too let go.
If the relationship is genuine both people will find a way back to each other.
The reason most dont on here is because people are constantly trying to fix things or make things better. Let it go.