You'd need to define 'mild', how many cups of coffee per day?
For me it's probably 50mg of caffeine per day (usually 5 cups of decaf). Various google searches suggest up to 400mg of caffeine per day is 'safe' and not considered excessive.
What's your definition of 'too much'?
And this goes the crux of issue, you need calories to sustain yourself as well as all the necessary vitamins and minerals. If Lee has no objections then he should post what he eats in a week and I'll put this into Cronometer. LCHF diets (however marketed) have been shown over time to be non sustainable and detrimental to your health. But then again people love hearing that their bad habits if done a certain way are okay to do.
I'm not sure what part your arguing about as you've touched on about 5 different issues in those few sentences.
Calories are required to sustain yourself, so if you want to lose weight then you need to restrict calorific intake, expend more (do more exercise) or otherwise change calorific intake so that it is in deficit based on BMR and exercise.
LCHF is a form of calorie restriction but isn't combined with fasting. The specific 'thing' about fasting (compared to just changing what you eat) is how it avoids the insulin spikes that hinder fat metabolism.
The majority of people moving off a LCHF regimen after losing weight will tend to slowly put it back on over time as they return to their previous calorific intake (but due to their weight loss their BMR is now lower than before, so eating what they used to eat slowly returns them to that original weight).
Those who've fasted regularly find it much easier to (subconsciously) reset their calorific intake based on their new BMR, so they are more likely to keep the weight off.
Appropriately chosen foods, even if eaten as part of a restricted calorie regimen, will still provide the necessary vitamins and minerals. I don't think of calorie deficits at the daily level any more, it's more of a weekly balance check, since fasting days have 0-350kcal intake and the day when the fast ends I may eat more than a 'normal' day. The point is that over time I'm running a accumulating deficit.
I agree that perpetual calorific deficit is not sustainable, but that's not what happens. When I'm lighter I tend to do a lot more exercise (increased marathon training, more cycling, etc) and more intensive. My calorific intake may increase but this in response to the increase demands from exercise. I can still fast regularly and not run a deficit. The body does not fall apart if it receives it's 7 days worth of calories in 5 days with 2 days fasting along the way, the concept of having to eat a certain amount per solar day is an entirely artificial construction.