Hiya Oobs and a massive welcome to you.
I have heard of others that dose as you do and also the CWE technique. At least you are not getting super high doses of ibuprofen which will sure help. However you are still getting 825 mg of codeine which I am sure you know is converted by the liver to a morphine equivalent so as far as withdrawal timeline etc it will probably run along the same lines as most of us. Having said that, we are all different and respond in different ways.
The symptoms you have noted seem to be similar to what I experienced. I too never had restless legs but did have stomach issues.
I think the main thing is you are here and fighting so that is amazing. Well done. I found after day 4 I just needed to get through the days. I still felt horrible and that took a little time to lift. I am day 29 today and still plagued by sleep/anxiety but that could possibly be other issues causing that too.
Stick around and we will support you as much as possible xx