Well I've never felt sick when high (except on legal opiates!) but I have felt sick for stretches of time when I can only assume I had 'excess acid'. That was a horrible sick and hungry feeling after food and it went away with a decent antacid (ranitidine or similar - not just a couple of Rennies). You could try that?
Yes. It doesn't look like it's related to the diabetes necessarily and if you've tried the usual treatments without success... Perhaps your GP could check for H.Pylori and anything else that might be relevant.