No need to withdraw from butter, but if you cut carbohydrates too quickly then yes you can suffer some symptoms, it is often caused by dehydration as carbs hold on to fluids but when you reduce them you lose that fluid which is often why people can lose weight quite quickly in the first couple of weeks.Are there withdrawal symptoms from food items , ie butter and sugar?
Crumpets are surprisingly high carb given they are full of holes. A small crumpet 45g is about 17g carb.I stopped eating 2 crumpets with lashings of butter a day (3/4 months) to get my cholesterol down - it worked. And cut right down on sugar to try and control the peaks and troughs. As you say, it was probably too drastic
Everybody is different but many find that by reducing carbs it has a beneficial effect on their cholesterol and the Low carb high fat should be interpreted as normal healthy fat and just not low fat.
Have a look at this link as there is good explanation and some do's and dont's, but is a low carb approach based on REAL food. https://lowcarbfreshwell.co.uk/
Don't forget you are only in the 'at risk' zone so modest changes are probably all that is needed.