Hi Honey! That's great that his nights are better!
Can you post your rutine right now? If I am correct you are now on 14,5h days so a long one! If it suits him, I wouldn't change! The question is if it suits you. I like to have some time in the evening for myself:).
If you decide to shorten first nap, I would be tempted not to cut/prolong any A time in the morning or after nap. I would go for the same routine as you have but shorten nap by 0,5h and than go for 3,5-4h after second nap. And I would tweak until you find a good, suitable for you and tour family balance between WU/BT.
Than you know to which strategy you will go when approaching 2:1 transition. Shortening first nap:).