... I already explained that we do not lose fifty percent of our security at the halving, since the exchange rate also effects this dynamic ...
Not really. This year, we are paying roughly 10% of Bitcoin's total value, or what people here call "market cap," to secure it. In other words, we are currently spending roughly a dime to store (secure) a dollar for a year.
After the halvening, we will be paying only a nickel.
It doesn't matter how much a dollar is worth, the ratio remains the same.
Same for efficiency/cost of mining gear.