Hi Patrick, sorry you are struggling so much. it is tough, and the this is for life thing hits us all sooner or later.
You said you like potatoes: I may have an answer for that.
Have you tried pre-cooking and reheating them? Apparently cooking, cooling and reheating changes the starch in some way so that it produces less of a BG spike. Its called resistant starch.
There are some posts on here about it. Try a search for more details.
Try boiling some and roasting a couple the next day. See how this affects BG. Of course you still cant eat a plateful - but some is better than none.
Hope this suggestion helps. you have done so well, with all you different problems, please dont give up now.