With the triatlon training the carbs from the potatoes should be good for you, and you are right to listen to your body
If you substitute the lean meat for fattier meat it is cheaper, and the fat will keep you more satiated
And change the egg whites to whole eggs, no need to avoid the yolk. And you could change the skimmed milk in your coffee to cream.
I changed cold turkey without a problem, I didn't get carb flu, but do what feels best for you.
Maybe berries like blueberries will work for you as fruit, they are low in sugar.
Overall it looks like you are doing a great job already