I guess I misunderstood too... So you're saying we aren't accumulating transaction fees since December. The only transaction fees that are paid out are those that are part of the block that is found by us. Is that right?
Yes, the only way to get any income with mining is to find/create new blocks. The income from mining a block is the combination of new coins that are created with the block, and the transaction fees of all the transactions in the block.
When you create a new transaction because you want to pay someone, it just floats around on the bitcoin peer-to-peer network. It is not part of the permanent ledger that is the blockchain. To anyone observing the transaction it is merely an intention to pay, which may take place in the future. Another transaction sending the same coins somewhere else might become part of the blockchain instead. This transaction is considered unconfirmed. You might trust it to pay a cup of coffee, but not a car (certainly not a Lambo).
So you offer a transaction fee on your transaction, to incentivize miners to include it in a block. The miners mine a block with your transaction, they get paid and now your transaction is in a block. Your transaction is in the block at the top of the chain. It has 1 confirmation, which is the block it is in. It's somewhat more trustworthy. But what if there is a blockchain fork and the other side of the fork becomes the longest chain? Then this transaction may yet disappear. This becomes less likely as more blocks are added on top of the block with the transaction. Once there are 5 additional blocks the transaction is said to have 6 confirmations. This is often considered to be the point where you can assume it is a permanent part of the blockchain. The recipient can trust that the coins you sent them are now theirs. This is what you paid the miners for.
Is there some explanation other than a long run of bad luck for why this is taking so long? Has difficulty jumped that much higher? Other variables?
Currently the difficulty is almost 3.3 trillion (called billion in continental europe). This means it takes a tremendous amount of work to find a block. On average it takes 3.3 trillion (mining pool proofs of) work. If the difficulty goes up the average time to find a block goes up. If our hashpower goes up the average time to find a block goes down.
Compared to 3 months back, the difficulty is now 2.5x what it was. Our hashpower is 3.5x what it was. So our average time to find a block has gone down. Further increasing the hashpower will further reduce the time to find blocks. It makes all rounds (time between blocks) go by faster, but most importantly of course the long and unlucky ones.
Our amount of work since the last block is over 10.6 trillion. That's more than 3x the difficulty and is certainly bad luck. This is fairly rare.
The worst block we've had took an amount of work that was 11x the difficulty. This is the awful block of which we do not speak. Except I just did. Thankfully something like that is extremely rare.