I'm lucky I seem able to tolerate most medicines, and with a cholesterol in the high 7s accepted that statins were the best option. they have brought it down to 5.5ish and it now seems stable and the doctors aren't pushing any further tablets to get it down more, they even say that the side effects of anything stronger is worth the limited benefit. They also have agreed to reduce my Metformin after my last HBA1C, so there are good HCP out there.
You say low carbing doesn't work for you, I would ask how low you are trying to go with the carbs. I manage at about 100 - 120g of carbs a day and still have managed to bring my BS levels down considerably. I still consider I have a balanced plate I just hadn't realised how many carbs I was eating. it might be worth adding yours up and seeing if a small reduction could help and then slowly reducing the amount until you find a balance between your BS and your stomach problems.
The other suggestion is a supplement like Psyllium Husks which I found very good for dealing with the side effects of Metformin.