The miners decides on the mining fee that they want to include into their block. You can try to convince miners to have the fees bind to the average fees but that probably would never work. Transaction fees are still very small compared to other payment methods.
I had issues with the tx fee quite a few times. Normally I pay a uniform transaction fee of
BTC0.0001, no matter how much the size of my transaction. Sometimes, the transaction can be quite big (10 KB or 15 KB), and on such occasions, I had to wait up to 48 hours to get the 3 confirmations. This can be a serious issue in the future. As Bitcoin gets older, the coins will be traded more and more, and the size will get bigger and bigger for each transaction. In such cases, the miners will simply refuse to transmit the transaction, if we are paying only the standard transaction fee of
BTC0.0001.
That should happen. If your TX is 10kb, you should be paying 0.001BTC as a fee (unlikely that it's going to happen unless you hoard LOADS of UXTOs. Miners want to utilize the 1mb that they are allowed to have with the best efficiency. If you have a fee of 0.0001BTC with a 10kb size and someone else have 0.00002BTC fee and 1 kb size, they would most likely be considering to accept the 1kb TX first.
There are always exception however. If every single miner dislike your address/coins/transaction, they can choose not to mine it no matter how much you pay. That's why we don't like mining centralisation.
The size will not increase no matter how much times it is "spent". (I can't go technical here.)
What are you talking about here and what you mean "unpredictable" ? Fees are already low comparing to the other payment methods (0.0001 BTC = 0.05$) .
To pay from exchange it's 0.0005-0.001 BTC = $0.25-$0.5, for a rate of $5000/BTC it's $2.5-$5.
Then stop using that exchange. The minimum fee for nodes to relay will get lowered if that happens. After sometime, less people would be willing to pay that high of a transaction fee and miners would start to mine transactions with lower TX fees.
