3) Despite the 'spreads' between block validations, in the long term the protocol adjusts to the average 600 s block time, so I suppose that it is unnecessary - even wrong - to use a block time variable other than 10 mins. Is that correct?
You are correct, using 10 mins block time is the only
accurate number.
1) Beside the network difficulty (i), the mining hash rate (ii), and the block time (iii), the certain exchange rates (iv), and the power consumption indicators (v) is there any other parameter that could increase the precision of a real-time mining calculator?
Indeed, there is the most important factor in regards to mining which is "PRICE", in fact nearly everything aside from bitcoin price is nearly irrelevant as far as mining profitably is concerned, the only way for the latter be wrong is if we could
increase the block rewards.
To elaborate more, assuming the rewards are 1
BTC per block and bitcoin worth $110,000, mining profitability would be the same as it is now with rewards at 12.5
BTC per block and price ranging around 8800$, and since mining rewards don't increase, it's safe to assume that prices make up to 99% of the factors involved.
Based on that, I sadly have to tell you that whatever you are trying to do is pretty much useless, unless you have a crystal ball that tells you what will bitcoin price be in the future.
I have made a similar thread '
For how long can we actually mine' where I made a simple calculation showing what
should the price of bitcoin be at every coming halving for mining to be as profitable as it is at the time of writing the topic, you can use the excel sheet in that topic to get the dates and rewards of all remaining halvings.
For instance, in 2033 where block rewards will be 0.78
BTC per block - price per bitcoin
should be $122,000 for mining to be as profitable, but we don't know the price of bitcoin in 2033, we also don't know the difficulty which can also be ignored because difficulty is purely based on price ( or at least this is what I think).
I hope my comment won't let you down, but what you are trying to do is actually speculate, you CAN"T calculate something you don't know.