OP, please stop listening to all pp on here (including me if I inadvertently do it) who tell you what he is doing, and what his motives are/were, and who even tell you what and why you are doing something. Only you know what is in your head and heart, and yes you are probably confused, but listening (reading) other peoples assumptions on here, will I feel - but I don't/can't know either - just make you even more confused. And your partner is the only one who knows what is in his heart/head, all these pp telling you what his motives are, really have NO idea, they are just advising from their personal experiences, and their own agendas.
Again, I feel (but I have no idea really) that you should spend some time with your own thoughts, and some time with your partner, discussing everything that occurs/worries you, then maybe have a time apart (both of you choose how long, but I would suggest at least a day, and a period of time when you can both individually concentrate on your thoughts, and when if at all possible, neither of you will be interrupted by anybody, except for emergencies). During this time I suggest you both have pen and paper readily available to jot down any other concerns/questions for the other one, that you had either forgotten about, or not thought of before.
The picture in my head for either/both of you, is not you sitting down at a table at 9.00am until 6.00pm staring at a piece of paper and trying to force yourself to do this exercise, if I had ever tried that, my mind would have gone completely blank, and I would have only managed to wind myself up even more - but maybe you thrive under that sort of pressure? We are all different, and knowing are own minds can be so difficult, which is why even attempting to know what is in some strangers mind, and not even directly from them, but through someone elses description over the internet, just seems almost impossible to me.
Like you I (used - I am disabled now) love walking, especially with a dog or two, and I could usually think well on a walk, with a sit down and my back leaning against a tree trunk for a rest. If I wanted to think and make notes, I would wear a light back pack with a drink or two in it, and maybe a snack, and a notebook and pen to jot notes down too. When my exDH left me (leaving me with our small children, one a new born baby), I was lucky enough to live near the sea, and every weekday morning after dropping the oldest at school, and leaving the youngest with my wonderful Mum, I would sit in my car by the sea for half an hour,, watching the world go by (popular year round tourist location), and the waves meander or crash against the shore, and just let my mind wander. I would usually think about my DxH, and me, and the life we had had, or him and the woman he left me for, and of course always my children and how they seemed to be coping. I would sometimes cry, but often I just felt the wonder of the sea, smell the fresh sea air, and actually feel quite peaceful despite my heartbreak. In a way I was luckier than you, as I didn't have any decisions to make about my DX, as he had made that decision, I was given no choice in it (of course in the next weeks, months and years I had lots of decisions to make, but this isn't supposed to be about me!) Anyway, that would have been another perfect time to have a notepad and pen with me, if I had had decisions to make. Maybe you could go to a nearby town, but not your own where you could be likely to meet people you know, and go into a cafe after a walk in a park, and sit with a cuppa, and just jot down any thoughts or feelings you had. Another thing I do when I am stressed, or have a decision to make, is keep a pen and paper by my bed, so that I could jot down any thoughts that were keeping me awske, or any pertinent dreams I had just had - that notepad being there realky helped me sleep, as I wasn't worried about forgetting spmetjing important I thought about. If you have the house to yourself, yoi could let your mind wander while you are vacuuming, or sit and listen to some music, but have that notepad handy. My God, I wonder if you are still reading this, if you ever started; but please if nothing else, please consider that no-one else knows what will make you happy, what decisions you should make, and there are no guarantees that anything you do decide to do will or will not make you happy in the long run. And the same goes for your partner, no-one on here, even you, knows what is in his heart, what his motivations are, BUT you have much more of an idea about that than we do, and you can talk to him, ask him things, we can't. So please don't be swayed by anyone here, follow your brain, heart AND your gut, and if you don't recognise a gut instinct yet, try to do the sort of things that might help you recognise and understand yours. Good luck OP, in the end, quite a bit might just rest on luck.