I am so sorry you are having so much trouble. How frustrated you must be. Now, I don't claim to know the answer - but I'm glad to share my experience and thoughts with you.
Naturally, dogs will not soil where they "live". They learn to control it as they get older. 8.5 mos is plenty old enough to control pee and poop for several hours - at least 6-8 hrs. So, I suggest an ex-pen (4x4 pen) for when your're gone. Its big enough they can walk around and stretch, but small enough that they can't get away from their waste - which should result in your baby holding it until his/her next walk. A gated off room(s) is too big - at least at this age.
Once you have control over when and where he/she poops, then clean it up immediately. We have three acres and we always clean up after Bailey.
I've heard several remedies on this website - and you've tried most of them. My personal experience - Bailey ate/played with her poop when I fed her commercial dog food. Now I feed her a homemade raw recipe which includes Potassium.
Please do your research and check around because I am a novice - but I believe that Bailey ignores her poop, now, because raw gets fully digested and because one ingredient is potassium.
A little funny - as I mentioned, we have three acres and her little poop gets lost very easily. If we take our eyes off the very spot - then its becomes difficult to find it and toss it. She used to help us find if we asked her - but now she just walks away and watches us as if we are on an easter egg hunt. She truly is uninterested in her poop. Good for her, but bad when it falls deep in the grass
Good luck!!!