Acarbose is not often used nowadays due to the high prevalence of side effects and the availability of other oral agents such as the gliptins, SGLT-2 inhibitors and pioglitazone. But otherwise it is a useful drug cos no hypos or weight gain due to acarbose itself
100 mg is a big UK dose - I used to start on 25mg (half a tablet) and increase to 50 mg with each meal - it was rare for anyone to tolerate it.
Have you tried a 50 mg dose? As with most oral agents, as one increases the dose, the glucose lowering effct does not increase so much, but side effects do.
Best wishes