Great news, Machka!
But be prepared for a long haul. As he progresses and as he starts to remember his past life, the part that will be very hard on you, both to understand and accept is that for Rowen, there will be his life now and his life before; completely separate. He is now an infant with some strange knowledge that seems to have been absorbed by his brain in the womb. The life before was lived by someone else and slowly the film of that life played by a character resembling Rowan will become accessible arts of his memory. The separation between my current life and my previous life has become quite blurred, but it has now been a full 40 years.
Your biggest challenge may well be accepting that Rowan is only what he is now. He will grow and change, just as a kid grows and changes, but he may never merge with the Rowan of his past. (This isn't entirely bad. He will have opportunities to do what is near impossible for most; to experience events that have happened before for the first time. So events that may have had traumatic consequences the first time can be re-experienced as a true first time with a much better outcome.)
Do your very best to not have any expectations and not project anything from what you have witnessed. This is a long journey. Celebrate the good when it happens. Also do all you can to develop a pool of support so you don't have to ear out key people. I'm prediction Rowan will recover to close to before with an added layer of humanity. iF yo ucan stick it out, you will be a winner also. But be prepared. This road is going to take years. You know how to get a hold of me. I'm not going away (even if I leave this forum).
I wrote this here rather than in an E-mail so others with TBI friends and relatives can see it.
Ben