Hi Hun, thanks that's really helpful. Okay, so it looks to me like you have long term accumulated OT working alongside short term UT (for the day in question) Once you realise that the 2 often go together it makes it a lot easier, to figure out what's going on. I think he may be getting caught in an OT/UT loop too.
Are you aiming for a set A time or 5.5 hours
IIWM I would think about doing 5.5 to nap but shooting for a 12.5 hour day minimum (ie if the nap is 2 hours a 13 hour day, but shorter a 12.5 hour day) The early NW are often OT but it seems to me that he needs a longer day to sleep through, I hope
It is frustrating when every day is different Hun. There are 2 ways to approach it. Set A times to nap and BT (or flexible BT) or set nap/BT. For us set A times have always worked and it leads to set WU and nap times once OT is eliminated. Set nap/BT can be harder for a LO to cope with, as you often need to push them through OT, so it usually takes longer to work, but it can also work well allowing LO to reset their clock. It really is a matter of preference to be honest, or for some people a matter of fitting LO sleeps around the rest of the family and work commitments.
Hope this makes sense, any thoughts
x.